feat: Review & Commit View - Diff Viewer & Git Actions (#334)

## Summary
Implements #334: [Phase 3] Review & Commit View - Diff Viewer & Git Actions

- File tree panel showing changed files grouped by directory with change type icons
- Syntax-highlighted unified diff viewer with dual-column line numbers
- Quality gate badges (pytest, ruff, python-build) with PASSED/FAILED status
- Export patch modal with copy-to-clipboard and download
- AI-generated commit messages using heuristic analysis
- Git commit with file list and commit message
- PR creation form with title/body and success modal
- 3 new backend endpoints: /api/v2/review/diff, /patch, /commit-message
- 4 new API client namespaces: reviewApi, gatesApi, gitApi, prApi
- 24 new tests (9 backend + 15 frontend)

## Acceptance Criteria
- [x] File tree panel displays changed files grouped by directory
- [x] Unified diff viewer with syntax highlighting and line numbers
- [x] Navigation between files (prev/next + tree click)
- [x] Quality gate status badges
- [x] Export patch with copy/download
- [x] Commit message textarea with AI generation
- [x] Commit button with loading state
- [x] PR creation form with success modal
- [x] Review nav item enabled in sidebar
- [x] Types added to shared types file
- [x] API client namespaces for review, gates, git, PR
- [x] All new code lint-clean

## Validation
- Tests: All passing (9 backend + 15 frontend + sidebar test updated)
- Linting: Clean (ruff + ESLint)
- Code review: All feedback addressed (3 internal + 4 automated)
- Demo: All 12 acceptance criteria verified with live browser demo

Closes #334

Author: frankbria

codeframe/core/git.py

@@ -8,7 +8,8 @@
 """
 
 import logging
-from dataclasses import dataclass
+import re
+from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Optional
 
@@ -55,6 +56,27 @@ class CommitResult:
     files_changed: int
 
 
+@dataclass
+class FileChange:
+    """Per-file change statistics from a diff."""
+
+    path: str
+    change_type: str  # "modified", "added", "deleted", "renamed"
+    insertions: int = 0
+    deletions: int = 0
+
+
+@dataclass
+class DiffStats:
+    """Parsed diff statistics."""
+
+    diff: str
+    files_changed: int
+    insertions: int
+    deletions: int
+    changed_files: list[FileChange] = field(default_factory=list)
+
+
 # ============================================================================
 # Git Operations
 # ============================================================================
@@ -293,3 +315,163 @@ def is_clean(workspace: Workspace) -> bool:
     """
     repo = _get_repo(workspace)
     return not repo.is_dirty(untracked_files=True)
+
+
+def get_diff_stats(workspace: Workspace, staged: bool = False) -> DiffStats:
+    """Get diff with parsed statistics.
+
+    Args:
+        workspace: Target workspace
+        staged: If True, show staged changes; if False, show unstaged
+
+    Returns:
+        DiffStats with parsed per-file statistics
+    """
+    repo = _get_repo(workspace)
+    diff_text = get_diff(workspace, staged=staged)
+
+    if not diff_text.strip():
+        return DiffStats(diff=diff_text, files_changed=0, insertions=0, deletions=0)
+
+    # Use git diff --stat for accurate statistics
+    try:
+        if staged:
+            stat_output = repo.git.diff("--cached", "--numstat") if repo.head.is_valid() else ""
+        else:
+            stat_output = repo.git.diff("--numstat")
+    except git.GitCommandError:
+        stat_output = ""
+
+    changed_files: list[FileChange] = []
+    total_insertions = 0
+    total_deletions = 0
+
+    for line in stat_output.strip().split("\n"):
+        if not line.strip():
+            continue
+        parts = line.split("\t")
+        if len(parts) >= 3:
+            ins_str, del_str, file_path = parts[0], parts[1], parts[2]
+            ins = int(ins_str) if ins_str != "-" else 0
+            dels = int(del_str) if del_str != "-" else 0
+            total_insertions += ins
+            total_deletions += dels
+
+            # Extract per-file section from diff for accurate change type detection
+            file_section_match = re.search(
+                rf"diff --git a/.*? b/{re.escape(file_path)}\n(.*?)(?=diff --git|\Z)",
+                diff_text,
+                re.DOTALL,
+            )
+            file_section = file_section_match.group(0) if file_section_match else ""
+
+            change_type = "modified"
+            if "new file mode" in file_section:
+                change_type = "added"
+            elif "deleted file mode" in file_section:
+                change_type = "deleted"
+            elif "rename from" in file_section:
+                change_type = "renamed"
+
+            changed_files.append(FileChange(
+                path=file_path,
+                change_type=change_type,
+                insertions=ins,
+                deletions=dels,
+            ))
+
+    return DiffStats(
+        diff=diff_text,
+        files_changed=len(changed_files),
+        insertions=total_insertions,
+        deletions=total_deletions,
+        changed_files=changed_files,
+    )
+
+
+def get_patch(workspace: Workspace, staged: bool = False) -> str:
+    """Get patch-formatted diff for export.
+
+    Args:
+        workspace: Target workspace
+        staged: If True, show staged changes; if False, show unstaged
+
+    Returns:
+        Patch content as string (with full headers for git apply)
+    """
+    repo = _get_repo(workspace)
+
+    try:
+        if staged:
+            if repo.head.is_valid():
+                return repo.git.diff("--cached", "--patch", "--full-index")
+            return ""
+        else:
+            return repo.git.diff("--patch", "--full-index")
+    except git.GitCommandError as e:
+        logger.warning(f"Failed to get patch: {e}")
+        return ""
+
+
+def generate_commit_message(workspace: Workspace, staged: bool = False) -> str:
+    """Generate a commit message from the current diff.
+
+    Uses heuristic analysis of changed files and diff content to suggest
+    a conventional commit message. Does not require LLM.
+
+    Args:
+        workspace: Target workspace
+        staged: If True, analyze staged changes; if False, unstaged
+
+    Returns:
+        Suggested commit message string
+    """
+    stats = get_diff_stats(workspace, staged=staged)
+
+    if not stats.changed_files:
+        return ""
+
+    files = stats.changed_files
+    file_count = len(files)
+
+    # Determine primary action from change types
+    added = [f for f in files if f.change_type == "added"]
+    deleted = [f for f in files if f.change_type == "deleted"]
+    modified = [f for f in files if f.change_type == "modified"]
+
+    # Pick prefix based on dominant change type
+    if len(added) > len(modified) and len(added) > len(deleted):
+        prefix = "feat"
+        action = "add"
+    elif len(deleted) > len(modified):
+        prefix = "refactor"
+        action = "remove"
+    else:
+        prefix = "feat"
+        action = "update"
+
+    # Detect common patterns
+    test_files = [f for f in files if "test" in f.path.lower()]
+    if test_files and len(test_files) == file_count:
+        prefix = "test"
+        action = "add" if added else "update"
+
+    config_files = [f for f in files if f.path.endswith((".json", ".yaml", ".yml", ".toml", ".cfg", ".ini"))]
+    if config_files and len(config_files) == file_count:
+        prefix = "chore"
+        action = "update"
+
+    # Build description
+    if file_count == 1:
+        file_path = files[0].path
+        name = Path(file_path).stem
+        description = f"{action} {name}"
+    else:
+        # Find common directory
+        dirs = set(str(Path(f.path).parent) for f in files)
+        if len(dirs) == 1 and list(dirs)[0] != ".":
+            description = f"{action} {list(dirs)[0]} ({file_count} files)"
+        else:
+            description = f"{action} {file_count} files"
+
+    return f"{prefix}: {description}"

codeframe/ui/routers/review_v2.py

@@ -14,7 +14,7 @@
 
 from codeframe.core.workspace import Workspace
 from codeframe.lib.rate_limiter import rate_limit_standard
-from codeframe.core import review
+from codeframe.core import review, git
 from codeframe.ui.dependencies import get_v2_workspace
 
 logger = logging.getLogger(__name__)
@@ -71,6 +71,38 @@ class ReviewTaskRequest(BaseModel):
     files_modified: list[str] = Field(..., min_length=1, description="Modified files to review")
 
 
+class FileChangeResponse(BaseModel):
+    """Per-file change statistics."""
+
+    path: str
+    change_type: str
+    insertions: int
+    deletions: int
+
+
+class DiffStatsResponse(BaseModel):
+    """Response model for diff with statistics."""
+
+    diff: str
+    files_changed: int
+    insertions: int
+    deletions: int
+    changed_files: list[FileChangeResponse]
+
+
+class PatchResponse(BaseModel):
+    """Response model for patch export."""
+
+    patch: str
+    filename: str
+
+
+class CommitMessageResponse(BaseModel):
+    """Response model for generated commit message."""
+
+    message: str
+
+
 # ============================================================================
 # Review Endpoints
 # ============================================================================
@@ -205,3 +237,124 @@ async def review_files_summary(
     except Exception as e:
         logger.error(f"Failed to get review summary: {e}", exc_info=True)
         raise HTTPException(status_code=500, detail=str(e))
+
+
+# ============================================================================
+# Diff & Patch Endpoints (for Review & Commit View)
+# ============================================================================
+
+
+@router.get("/diff", response_model=DiffStatsResponse)
+@rate_limit_standard()
+async def get_review_diff(
+    request: Request,
+    staged: bool = False,
+    workspace: Workspace = Depends(get_v2_workspace),
+) -> DiffStatsResponse:
+    """Get unified diff with parsed statistics.
+
+    Returns the raw diff plus per-file change counts for display
+    in the Review & Commit View.
+
+    Args:
+        request: HTTP request for rate limiting
+        staged: If True, show staged changes; if False, show unstaged
+        workspace: v2 Workspace
+
+    Returns:
+        DiffStatsResponse with diff text and statistics
+    """
+    try:
+        stats = git.get_diff_stats(workspace, staged=staged)
+
+        return DiffStatsResponse(
+            diff=stats.diff,
+            files_changed=stats.files_changed,
+            insertions=stats.insertions,
+            deletions=stats.deletions,
+            changed_files=[
+                FileChangeResponse(
+                    path=f.path,
+                    change_type=f.change_type,
+                    insertions=f.insertions,
+                    deletions=f.deletions,
+                )
+                for f in stats.changed_files
+            ],
+        )
+
+    except ValueError as e:
+        logger.error(f"Get review diff failed: {e}")
+        raise HTTPException(status_code=400, detail=str(e))
+    except Exception as e:
+        logger.error(f"Failed to get review diff: {e}", exc_info=True)
+        raise HTTPException(status_code=500, detail=str(e))
+
+
+@router.get("/patch", response_model=PatchResponse)
+@rate_limit_standard()
+async def get_review_patch(
+    request: Request,
+    staged: bool = False,
+    workspace: Workspace = Depends(get_v2_workspace),
+) -> PatchResponse:
+    """Get patch-formatted diff for export.
+
+    Returns the diff in patch format suitable for `git apply`.
+
+    Args:
+        request: HTTP request for rate limiting
+        staged: If True, show staged changes; if False, show unstaged
+        workspace: v2 Workspace
+
+    Returns:
+        PatchResponse with patch content and suggested filename
+    """
+    try:
+        patch_content = git.get_patch(workspace, staged=staged)
+        branch = git.get_current_branch(workspace)
+        filename = f"{branch.replace('/', '-')}.patch"
+
+        return PatchResponse(
+            patch=patch_content,
+            filename=filename,
+        )
+
+    except ValueError as e:
+        logger.error(f"Get patch failed: {e}")
+        raise HTTPException(status_code=400, detail=str(e))
+    except Exception as e:
+        logger.error(f"Failed to get patch: {e}", exc_info=True)
+        raise HTTPException(status_code=500, detail=str(e))
+
+
+@router.post("/commit-message", response_model=CommitMessageResponse)
+@rate_limit_standard()
+async def generate_commit_message(
+    request: Request,
+    staged: bool = False,
+    workspace: Workspace = Depends(get_v2_workspace),
+) -> CommitMessageResponse:
+    """Generate a commit message from the current diff.
+
+    Analyzes changed files to suggest a conventional commit message.
+
+    Args:
+        request: HTTP request for rate limiting
+        staged: If True, analyze staged changes; if False, unstaged
+        workspace: v2 Workspace
+
+    Returns:
+        CommitMessageResponse with suggested message
+    """
+    try:
+        message = git.generate_commit_message(workspace, staged=staged)
+
+        return CommitMessageResponse(message=message)
+
+    except ValueError as e:
+        logger.error(f"Generate commit message failed: {e}")
+        raise HTTPException(status_code=400, detail=str(e))
+    except Exception as e:
+        logger.error(f"Failed to generate commit message: {e}", exc_info=True)
+        raise HTTPException(status_code=500, detail=str(e))