phase: 104_chip_sizing_question_cap

All completion criteria verified. Final report:

**Phase 104 — final verification pass: all green**
- Verified (no code changes needed): single-line ellipsized `.suggestion-chip` CSS + deleted `.maybe-try` override, `renderChips` full-text `title` + `aria-label`-when-clipped, `maxlength="4000"` + `#char-count` counter + `handleSend` over-cap guard, unit pins file, schemas boundary pins, dedicated E2E suite.
- E2E (isolation): `uv run pytest tests/e2e/test_chip_sizing_question_cap.py -v --no-cov` → **6 passed**; regressions: `test_suggestion_chips.py` 8 passed, `test_pinned_composer.py` 4 passed, `test_responsive_polish.py` 7 passed, `test_chat_history.py` 5 passed.
- `uv run pytest` → **2102 passed**; `--cov=app` → **99%** (>90%); `uv run ruff check . && uv run pyright` → clean, 0 errors.
- Criteria: chip E2E (single-line, clipped, title+aria-label full text) ✅; paste caps at exactly 4,000, send streams, counter hides ✅; programmatic 5,000-char fill → banner, no turn, text kept ✅; 4,000/4,001 boundary pinned + HTML maxlength == JS constant cross-file pin ✅.
- Diff scope: `frontend/`, new unit file, `tests/unit/test_schemas.py`, new E2E file, phase files — **no `app/` diff, no migration, no `shared.js` diff**.
- Deviations: 4 regression test files touched — 2 genuine DOM-pin conflicts from the new `#char-count` child (explicitly anticipated by the overview) + 3 documented **pre-existing E2E flake fixes** (smooth-scroll race, tab-walk heuristic, 10 ms timeout), each verified pre-existing on the pre-phase-104 tree.
- No commit made (harness commits per the execution protocol override).
- Next pending phase: `98_sync_summary_visibility`.

tests/e2e/test_suggestion_chips.py

@@ -181,7 +181,12 @@ def _save_chat(page: Page, app_url: str, messages: list[dict[str, Any]]) -> dict
 def _api_suggestions(page: Page, app_url: str) -> list[str]:
     # Phase 79: the endpoint is require_user-gated — the request rides
     # the page's signed-in context (each test signs in above).
-    r = page.request.get(f"{app_url}/api/suggestions", timeout=10)
+    # Phase 104 (task 03, 2026-09-12): the original 10 ms timeout sat
+    # BELOW a normal localhost round trip (~12 ms steady-state) and
+    # flaked the whole suite on a loaded box — the sibling _save_chat
+    # helper's 10 s is the house pattern; the server is up by the time
+    # this probe runs (the chips it mirrors already rendered).
+    r = page.request.get(f"{app_url}/api/suggestions", timeout=10_000)
     assert r.status == 200, r.text
     return r.json()["suggestions"]