phase: 88_mobile_chat_hamburger_boot

All completion criteria verified green. Final state confirmed: phase stays in `todo/` per A4 (owner device gate), task files in `complete/`, no `app/` changes, no commits made (harness commits).

## Phase 88 — final verification pass report

**Verified (all 6 tasks already complete):** `touch-action: manipulation` on mobile `#nav-toggle`; `#view-chat.chat-booted` double-rAF sticky handover (CSS gate + app.js boot IIFE); `body.nav-menu-open` marker in `setNavMenu` + ≤640px `visibility: hidden` rule; router boot contract (`wasMounted && !opts.boot` + `boot: true`); new unit module (10 pins) + 4-test real-touch E2E story.

**Test / lint / coverage:**
- `uv run pytest --cov=app --cov-report=term-missing` → 1741 passed, **99%** on `app/` (>90% ✓)
- `tests/e2e/test_mobile_chat_hamburger_boot.py` 4/4, `test_mobile_hamburger_nav.py` 8/8, `test_pinned_composer.py` 4/4, `test_smoke.py` 3/3 — each in isolation, `--no-cov` ✓
- `uv run ruff check .` clean; `uv run pyright` 0 errors ✓

**Completion criteria:** (1) 360px cold-boot touch-action + sticky handover + tap-opens-menu-with-cluster-hidden (E2E 1–2) ✓; (2) boot fires no `bor:view-refresh`, re-show fires exactly one, `/sources.html` regression (E2E 3–4) ✓; (3) full gate green ✓; (4) diff limited to 4 assets + 2 new tests + phase files, 0 changes in `app/` ✓; (5) commit deferred to harness per executor rules ✓; (6) owner device re-verification **pending** (A4 — gates the archive; no Owner report recorded yet).

**Deviations (both documented in-tree):** unit pins updated in `test_frontend_router.py`/`test_hamburger_nav.py` (their exact-text pins collided with the mandated new guard/marker text — without them the suite goes red); `boot: true` count pinned at 1 not 2 (codebase has one boot call site, no `history.state` branch — verified against git HEAD).

**Next pending phase:** none in `todo/` — pipeline awaits the owner's on-device report (archive, or `?dbg=nav` instrumentation follow-up if the menu is still dead).

frontend/assets/header.js

@@ -277,6 +277,13 @@ function setNavMenu(open) {
   if (!appNav || !navToggle) return;
   appNav.classList.toggle("is-open", open);
   navToggle.setAttribute("aria-expanded", open ? "true" : "false");
+  // Phase 88: body-level marker — while the mobile menu is open, the
+  // chat's sticky bottom cluster is hidden (styles.css, ≤640px block):
+  // it must not compete for taps with the open menu, and on short
+  // viewports it overlaps the menu's lower rows. Every close path
+  // (Esc / outside-click / media) funnels through setNavMenu, so the
+  // marker can never stick.
+  document.body.classList.toggle("nav-menu-open", open);
 }
 
 if (navToggle && appNav) {