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/unit/test_save_chat_ui.py

@@ -695,8 +695,10 @@ def test_chat_actions_wrapper_holds_both_pills_in_order() -> None:
     phase 65 (2026-09-01, ``TODO.md`` L3, owner confirmation) moved it
     from the top of the column to the bottom: below the ``#messages``
     section, directly above the composer; nothing but the row's own
-    comment lands between ``#messages`` and the row, and nothing but
-    the composer comment lands between the row and the composer. No
+    comment lands between ``#messages`` and the row, and nothing but the
+    phase-104 ``#char-count`` counter + the composer comment lands
+    between the row and the composer (the counter is hidden by default —
+    zero height, the pinned-cluster geometry untouched). No
     other page carries ``.chat-actions`` (chat-page only, like the
     pills)."""
     html = _index()
@@ -730,12 +732,23 @@ def test_chat_actions_wrapper_holds_both_pills_in_order() -> None:
         and "<form" not in between
     ), ("nothing but the row's comment lands between #messages and the row")
     after = html[end:composer_idx]
+    # Phase 104 (owner 2026-09-12): the ONE permitted child between the
+    # row and the composer is the hidden-by-default question-length
+    # counter — everything else (ids, buttons, sections, forms) is
+    # still excluded from the gap.
+    after_minus_counter = after.replace(
+        '<p class="char-count" id="char-count" hidden></p>', ""
+    )
     assert (
-        "id=" not in after
-        and "<button" not in after
-        and "<section" not in after
-        and "<form" not in after
-    ), ("nothing but the composer comment lands between the row and the composer")
+        after.count("<p") == 1
+        and "id=" not in after_minus_counter
+        and "<button" not in after_minus_counter
+        and "<section" not in after_minus_counter
+        and "<form" not in after_minus_counter
+    ), (
+        "nothing but the phase-104 counter + the composer comment lands "
+        "between the row and the composer"
+    )
     # Phase 76 (task 02): the folded view files are gone (the shell's
     # chat view is the one and only carrier of the row — pinned above);
     # the standalone pages carry none (task 03 dropped the last folded