feat(desktop): add diff review commit flow

.qwen/e2e-tests/electron-desktop/diff-review-commit.md

@@ -0,0 +1,63 @@
+# Electron Desktop E2E Record: Diff Review and Commit
+
+Date: 2026-04-25
+
+## Slice
+
+Slice 12 basic diff review and commit.
+
+## User-Visible Scenario
+
+1. Launch the desktop app with a temporary HOME/QWEN_RUNTIME_DIR and fake ACP.
+2. Open a temporary Git workspace with an initial commit.
+3. Modify a tracked file and create an untracked file.
+4. Verify the right Review panel lists changed files and textual diff content.
+5. Stage all changes from the Review panel.
+6. Enter a commit message and commit.
+7. Verify the Review panel returns to a clean state.
+
+## Assertions
+
+- `GET /api/projects/:id/git/diff` returns modified and untracked files.
+- The Review panel shows changed file count and diff text.
+- `POST /api/projects/:id/git/stage` updates Git status from modified/untracked
+  to staged.
+- `POST /api/projects/:id/git/commit` creates a commit and returns a clean
+  status.
+- `POST /api/projects/:id/git/revert` cleans tracked and untracked changes when
+  explicitly invoked.
+- Commit and Git errors are displayed in the review area.
+
+## Diagnostics on Failure
+
+- Save renderer screenshot.
+- Save renderer console errors and failed network requests.
+- Save Electron main stdout/stderr.
+- Save `git -C <workspace> status --porcelain=v1 --branch`.
+- Save `git -C <workspace> diff` and `git -C <workspace> diff --cached`.
+- Save DesktopServer responses for diff/stage/revert/commit routes.
+
+## Automated Coverage Added This Iteration
+
+The full Electron E2E harness is still pending. This iteration added
+server-level coverage in `packages/desktop/src/server/index.test.ts`:
+
+- opens a registered project and reads `/git/diff`;
+- verifies modified and untracked files are returned with diff text;
+- stages all changes and verifies status counts;
+- commits staged changes and verifies a clean status;
+- reverts all changes and verifies the workspace returns to the initial file
+  content.
+
+## Execution Results
+
+- `npm run test --workspace=packages/desktop` passed: 8 files, 50 tests.
+- `npm run typecheck --workspace=packages/desktop` passed.
+- `npm run lint --workspace=packages/desktop` passed.
+- `npm run build --workspace=packages/desktop` passed.
+
+## Remaining Risk
+
+Hunk-level accept/revert, inline comments, Open in Editor, and real Electron
+renderer assertions are not complete yet. They remain required before the MVP
+can be marked done.