feat(cockpit): quick wins — sync chip, cost budget guard, digest, recent commits (W3)

Four small, high-delight features that turn passive capture into glanceable signals.

- Sync chip on project cards: ahead/behind vs upstream + last-commit time, folded
  into the existing concurrent per-repo metadata pass (git rev-list --count
  --left-right @{u}...HEAD + git log -1 --format=%ct; no upstream → undefined, no route).
- Cost budget guard: COST_BUDGET_USD env (0 = off); a per-session one-shot latch
  (Session.budgetNotified, cost is monotonic so never re-armed) fires a single push
  on threshold crossing in manager.handleStatusLine; the already-broadcast telemetry
  frame carries the warn (tg-cost-warn styling derived from costUsd>=budget via
  /config/ui — no new ServerMessage). web-push title added to sw-push.js.
- "While you were away" digest: GET /digest?since= → {finished, needsInput, stuck,
  totalCostUsd, sessions[]} aggregate over manager.list(); FE banner on reconnect.
- Recent commits per project: src/http/git-log.ts (NUL-delimited git log → CommitInfo[]),
  GET /projects/log?path= (isValidGitDir), textContent-inert render in project detail.

All git via execFile (no shell) + validated cwd; new routes read-only; commit
messages rendered via textContent. Verified: typecheck + build:web clean, 1904 pass
at --test-timeout=30000 (two default-5s failures are slow-sandbox real-subprocess
timeout flakes — the known ring-buffer test + a new real-git-clone sync test — not
logic regressions).

test/projects-panel.test.ts

@@ -33,6 +33,7 @@ const {
   toggleFav,
   normalizeProject,
   makeProjectCard,
+  makeSyncChip,
   renderProjectDetail,
   groupProjects,
   displayLabel,
@@ -285,6 +286,65 @@ describe('normalizeProject', () => {
     expect(p?.lastActiveMs).toBeUndefined()
     expect(p?.isGit).toBe(false)
   })
+
+  it('passes through numeric sync fields (W3 a)', () => {
+    const p = normalizeProject({ name: 'web', path: '/p', ahead: 2, behind: 1, lastCommitMs: 123456 })
+    expect(p?.ahead).toBe(2)
+    expect(p?.behind).toBe(1)
+    expect(p?.lastCommitMs).toBe(123456)
+  })
+
+  it('drops non-numeric sync fields (W3 a)', () => {
+    const p = normalizeProject({ name: 'web', path: '/p', ahead: '2', behind: null, lastCommitMs: 'x' })
+    expect(p?.ahead).toBeUndefined()
+    expect(p?.behind).toBeUndefined()
+    expect(p?.lastCommitMs).toBeUndefined()
+  })
+})
+
+/* ── makeSyncChip / sync chip on the card (W3 a) ─────────────────────────────── */
+
+describe('makeSyncChip', () => {
+  it('renders ↑ahead ↓behind when there is drift', () => {
+    const chip = makeSyncChip(makeProject({ ahead: 2, behind: 1 }))
+    expect(chip).not.toBeNull()
+    expect(chip?.className).toContain('proj-sync')
+    expect(chip?.textContent).toBe('↑2 ↓1')
+  })
+
+  it('shows only the ahead arrow when behind is 0', () => {
+    const chip = makeSyncChip(makeProject({ ahead: 3, behind: 0 }))
+    expect(chip?.textContent).toBe('↑3')
+  })
+
+  it('returns null when in sync (ahead=behind=0)', () => {
+    expect(makeSyncChip(makeProject({ ahead: 0, behind: 0 }))).toBeNull()
+  })
+
+  it('returns null when ahead/behind are undefined', () => {
+    expect(makeSyncChip(makeProject())).toBeNull()
+  })
+
+  it('includes the last-commit time in the tooltip when present', () => {
+    const chip = makeSyncChip(makeProject({ ahead: 1, lastCommitMs: Date.now() - 3600_000 }))
+    expect(chip?.title).toContain('last commit')
+  })
+})
+
+describe('makeProjectCard — sync chip', () => {
+  const noopHooks = () => ({ onOpenProject: vi.fn(), onEnterSession: vi.fn() })
+
+  it('renders the sync chip when the project has drift', () => {
+    const card = makeProjectCard(makeProject({ ahead: 2, behind: 1 }), new Set(), noopHooks(), () => {})
+    expect(card.querySelector('.proj-sync')?.textContent).toBe('↑2 ↓1')
+  })
+
+  it('omits the sync chip when in sync / undefined', () => {
+    const inSync = makeProjectCard(makeProject({ ahead: 0, behind: 0 }), new Set(), noopHooks(), () => {})
+    expect(inSync.querySelector('.proj-sync')).toBeNull()
+    const noData = makeProjectCard(makeProject(), new Set(), noopHooks(), () => {})
+    expect(noData.querySelector('.proj-sync')).toBeNull()
+  })
 })
 
 /* ── makeProjectCard launcher row (Claude · Codex · VS Code) ────────────────── */