feat: git panel redesign (#535)

* feat(git-panel): add Branches tab, Fetch always visible, inline error banners

- Add dedicated Branches tab (local/remote sections, switch with confirmation, delete branch, create branch)
- Rename History tab to Commits; add change-count badge on Changes tab
- Fetch button always visible when remote exists (not only when both ahead & behind)
- Inline error banner below header for failed push/pull/fetch, with dismiss button
- Server: /api/git/branches now returns localBranches + remoteBranches separately
- Server: add /api/git/delete-branch endpoint (prevents deleting current branch)
- Controller: expose operationError, clearOperationError, deleteBranch, localBranches, remoteBranches
- Constants: add deleteBranch to all ConfirmActionType record maps

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix: git log datetime

* feat(git-panel): add staged/unstaged sections and enhanced commit details

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Haile <118998054+blackmammoth@users.noreply.github.com>

src/components/git-panel/utils/gitPanelUtils.ts

@@ -24,3 +24,70 @@ export function getStatusLabel(status: FileStatusCode): string {
 export function getStatusBadgeClass(status: FileStatusCode): string {
   return FILE_STATUS_BADGE_CLASSES[status] || FILE_STATUS_BADGE_CLASSES.U;
 }
+
+// ---------------------------------------------------------------------------
+// Parse `git show` output to extract per-file change info
+// ---------------------------------------------------------------------------
+
+export type CommitFileChange = {
+  path: string;
+  directory: string;
+  filename: string;
+  status: FileStatusCode;
+  insertions: number;
+  deletions: number;
+};
+
+export type CommitFileSummary = {
+  files: CommitFileChange[];
+  totalFiles: number;
+  totalInsertions: number;
+  totalDeletions: number;
+};
+
+export function parseCommitFiles(showOutput: string): CommitFileSummary {
+  const files: CommitFileChange[] = [];
+  // Split on file diff boundaries
+  const fileDiffs = showOutput.split(/^diff --git /m).slice(1);
+
+  for (const section of fileDiffs) {
+    const lines = section.split('\n');
+    // Extract path from "a/path b/path"
+    const header = lines[0] ?? '';
+    const match = header.match(/^a\/(.+?) b\/(.+)/);
+    if (!match) continue;
+
+    const pathA = match[1];
+    const pathB = match[2];
+
+    // Determine status
+    let status: FileStatusCode = 'M';
+    const joined = lines.slice(0, 6).join('\n');
+    if (joined.includes('new file mode')) status = 'A';
+    else if (joined.includes('deleted file mode')) status = 'D';
+
+    const filePath = status === 'D' ? pathA : pathB;
+
+    // Count insertions/deletions (lines starting with +/- but not +++/---)
+    let insertions = 0;
+    let deletions = 0;
+    for (const line of lines) {
+      if (line.startsWith('+++') || line.startsWith('---')) continue;
+      if (line.startsWith('+')) insertions++;
+      else if (line.startsWith('-')) deletions++;
+    }
+
+    const lastSlash = filePath.lastIndexOf('/');
+    const directory = lastSlash >= 0 ? filePath.substring(0, lastSlash + 1) : '';
+    const filename = lastSlash >= 0 ? filePath.substring(lastSlash + 1) : filePath;
+
+    files.push({ path: filePath, directory, filename, status, insertions, deletions });
+  }
+
+  return {
+    files,
+    totalFiles: files.length,
+    totalInsertions: files.reduce((sum, f) => sum + f.insertions, 0),
+    totalDeletions: files.reduce((sum, f) => sum + f.deletions, 0),
+  };
+}