🤖 refactor: remove file explorer (#3208)

Summary

Removes the right sidebar file explorer and its file viewer tab flow
wholesale. The sidebar now keeps only the remaining static tabs plus
terminal tabs, and persisted runtime layouts and saved layout presets
sanitize legacy explorer/file tabs instead of re-injecting or discarding
them.

Implementation

- Deleted Explorer/FileViewer components, tests, stories, cache, and
file-explorer utilities.
- Removed explorer/file tabs from sidebar tab types, tab
registry/labels, layout defaults, layout preset schemas, stories, CSS
theme tokens, and e2e split-layout expectations.
- Preserved legacy saved layout presets by stripping removed
explorer/file tabs during preset normalization.
- Kept a small file-read utility for immersive review's existing
file-content overlay path.

Validation

- `make static-check`
- `bun test src/common/types/uiLayouts.test.ts`
- `bun test src/browser/utils/fileRead.test.ts`
- `bun test src/browser/utils/rightSidebarLayout.test.ts`
- `bun test src/browser/contexts/WorkspaceContext.test.tsx`
- `make fmt-check`
- `make typecheck`
- `make lint`

Risks

Medium risk around persisted right-sidebar layout compatibility; legacy
explorer/file tabs are stripped at parse/normalization time and
removed-only tabsets fall back to Stats.

---

_Generated with `mux` • Model: `openai:gpt-5.5` • Thinking: `high` •
Cost: `536175{MUX_COSTS_USD:-0}`_

<!-- mux-attribution: model=openai:gpt-5.5 thinking=high costs=15.74 -->

Author: ammar-agent

src/browser/contexts/WorkspaceContext.test.tsx

@@ -733,7 +733,7 @@ describe("WorkspaceContext", () => {
         root: {
           type: "tabset",
           id: "tabset-1",
-          tabs: ["costs", "explorer", "terminal:t1"],
+          tabs: ["costs", "review", "terminal:t1"],
           activeTab: "terminal:t1",
         },
       };
@@ -759,10 +759,10 @@ describe("WorkspaceContext", () => {
         throw new Error("Expected cleaned right sidebar layout to be a tabset");
       }
 
-      // "explorer" becomes active because removeTabEverywhere picks the adjacent
+      // "review" becomes active because removeTabEverywhere picks the adjacent
       // tab after the removed terminal tab.
-      expect(cleanedLayout.root.tabs).toEqual(["costs", "explorer"]);
-      expect(cleanedLayout.root.activeTab).toBe("explorer");
+      expect(cleanedLayout.root.tabs).toEqual(["costs", "review"]);
+      expect(cleanedLayout.root.activeTab).toBe("review");
       expect(
         readPersistedState<Record<string, string>>(terminalTitlesKey, { stale: "title" })
       ).toEqual({});

src/browser/features/RightSidebar/CodeReview/HunkViewer.tsx

@@ -49,8 +49,6 @@ interface HunkViewerProps {
   includeUncommitted: boolean;
   /** Action callbacks for inline review notes */
   reviewActions?: ReviewActionCallbacks;
-  /** Callback to open a file in a new tab */
-  onOpenFile?: (relativePath: string) => void;
 }
 
 function renderHighlightedFilePath(
@@ -128,7 +126,6 @@ export const HunkViewer = React.memo<HunkViewerProps>(
     diffBase,
     reviewActions,
     includeUncommitted,
-    onOpenFile,
   }) => {
     // Ref for the hunk container to track visibility
     const hunkRef = React.useRef<HTMLDivElement>(null);
@@ -192,14 +189,6 @@ export const HunkViewer = React.memo<HunkViewerProps>(
       [hunk.filePath, searchConfig]
     );
 
-    const handleOpenFile = React.useCallback(
-      (event: React.MouseEvent<HTMLButtonElement>) => {
-        event.stopPropagation();
-        onOpenFile?.(hunk.filePath);
-      },
-      [onOpenFile, hunk.filePath]
-    );
-
     // Persist manual expand/collapse state across remounts per workspace
     // Maps hunkId -> isExpanded for user's manual preferences
     // Enable listener to synchronize updates across all HunkViewer instances
@@ -337,23 +326,9 @@ export const HunkViewer = React.memo<HunkViewerProps>(
               </TooltipContent>
             </Tooltip>
           )}
-          {onOpenFile ? (
-            <TooltipIfPresent tooltip={hunk.filePath} side="top" align="start">
-              <button
-                type="button"
-                onClick={handleOpenFile}
-                className={cn(
-                  "text-foreground min-w-0 truncate bg-transparent p-0 text-left",
-                  "hover:text-link focus-visible:text-link cursor-pointer border-none"
-                )}
-                aria-label={`Open ${hunk.filePath} in new tab`}
-              >
-                <span>{highlightedFilePath}</span>
-              </button>
-            </TooltipIfPresent>
-          ) : (
+          <TooltipIfPresent tooltip={hunk.filePath} side="top" align="start">
             <div className="text-foreground min-w-0 truncate">{highlightedFilePath}</div>
-          )}
+          </TooltipIfPresent>
           <div className="text-muted ml-auto flex shrink-0 items-center gap-1.5 whitespace-nowrap">
             {!isPureRename && (
               <>

src/browser/features/RightSidebar/CodeReview/ImmersiveReviewView.tsx

@@ -41,7 +41,7 @@ import {
   matchesKeybind,
 } from "@/browser/utils/ui/keybinds";
 import { stopKeyboardPropagation } from "@/browser/utils/events";
-import { buildReadFileScript, processFileContents } from "@/browser/utils/fileExplorer";
+import { buildReadFileScript, processFileContents } from "@/browser/utils/fileRead";
 import { TooltipIfPresent } from "@/browser/components/Tooltip/Tooltip";
 import {
   parseReviewLineRange,

src/browser/features/RightSidebar/CodeReview/ReviewPanel.tsx

@@ -107,8 +107,6 @@ interface ReviewPanelProps {
   isTouchImmersive?: boolean;
   /** Allow parent to switch touch/mobile immersive affordances before entering immersive UI. */
   onTouchImmersiveChange?: (isTouch: boolean) => void;
-  /** Callback to open a file in a new tab */
-  onOpenFile?: (relativePath: string) => void;
 }
 
 interface ReviewSearchState {
@@ -344,7 +342,6 @@ export const ReviewPanel: React.FC<ReviewPanelProps> = ({
   onStatsChange,
   isTouchImmersive = false,
   onTouchImmersiveChange,
-  onOpenFile,
 }) => {
   const originFetchRef = useRef<OriginFetchState | null>(null);
   const { api } = useAPI();
@@ -1733,7 +1730,6 @@ export const ReviewPanel: React.FC<ReviewPanelProps> = ({
                       diffBase={filters.diffBase}
                       includeUncommitted={filters.includeUncommitted}
                       reviewActions={reviewActions}
-                      onOpenFile={onOpenFile}
                     />
                   );
                 })