feat: mount parent .git for worktree resolution in reviewer container

Git worktrees reference the parent repo's .git directory via absolute
path. Without mounting it, all git commands fail inside the container.
Now reads the .git file, resolves the parent .git path, and mounts it
read-only at the same host path so references resolve naturally.

src/container-runner.ts

@@ -214,6 +214,37 @@ export function buildReviewerMounts(
     readonly: true,
   });
 
+  // Git worktree support: worktree's .git file references the parent repo's
+  // .git directory via absolute path. Mount the parent .git at the same host
+  // path so git commands resolve inside the container.
+  const dotGitPath = path.join(ownerWorkspaceDir, '.git');
+  try {
+    const stat = fs.statSync(dotGitPath);
+    if (stat.isFile()) {
+      // Worktree: .git is a file containing "gitdir: /path/to/.git/worktrees/name"
+      const content = fs.readFileSync(dotGitPath, 'utf-8').trim();
+      const match = content.match(/^gitdir:\s*(.+)$/);
+      if (match) {
+        const worktreeGitDir = path.resolve(ownerWorkspaceDir, match[1]);
+        // worktreeGitDir = /parent/.git/worktrees/name → parent .git = ../../
+        const parentGitDir = path.resolve(worktreeGitDir, '..', '..');
+        if (fs.existsSync(parentGitDir)) {
+          mounts.push({
+            hostPath: parentGitDir,
+            containerPath: parentGitDir,
+            readonly: true,
+          });
+          logger.debug(
+            { parentGitDir, worktreeGitDir },
+            'Mounting parent .git for worktree resolution',
+          );
+        }
+      }
+    }
+  } catch {
+    // Not a git repo or .git missing — skip
+  }
+
   // pnpm global store: mount at the same host path so hardlinks resolve.
   const pnpmStore = detectPnpmStorePath(ownerWorkspaceDir);
   if (pnpmStore) {