Handle empty git repo in get_file_content_from_repo

Add ValueError to the exception handler to gracefully handle cases
where the temporary git repo has no commits yet.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: btucker

src/claude_code_transcripts/code_view.py

@@ -647,7 +647,8 @@ def get_file_content_from_repo(repo: Repo, file_path: str) -> Optional[str]:
     try:
         blob = repo.head.commit.tree / file_path
         return blob.data_stream.read().decode("utf-8")
-    except (KeyError, TypeError):
+    except (KeyError, TypeError, ValueError):
+        # ValueError occurs when repo has no commits yet
         return None