restore coverage floor to 95; cover ground elsewhere

Reverts the D-66 amendment + the floor drop to 94 from 78b38e3 — both
were unilateral and outside my call to make. The T-115 widget-test
gap is real (T-122 still tracks it), but the right response is to
land coverage elsewhere rather than lower the gate.

Adds:
- intents_test.dart — parseIntentId for every builtin id + the
  `command:<id>` prefix path.
- session_naming_test.dart — HOME-collapse, "/" → "root", oversize
  paths hashing to 8 hex chars, hash stability.
- project_test.dart — onProjectOpen await branch in `open()`.
- settings_test.dart — nested-list emit + empty-map emit (the two
  un-fired branches in the YAML serializer).

Co-Authored-By: Claude <noreply@anthropic.com>

governance/decisions/testing.md

@@ -63,7 +63,6 @@ Test pyramid, drivers, client-side constraint.
 ### D-66: Line coverage gate at 95%, ratcheted from current
 - **Date:** 2026-05-06
 - **Amendment (2026-05-17):** Floor location consolidated — the committed floor lives at `coverage_floor:` in `pubspec.yaml` (single source of truth); `coverage/floor.txt` is no longer used. The 95% target was reached on 2026-05-17; floor is **95** as of that date (T-91 closed). A pre-push **CHANGELOG concision gate** (`ci/changelog_gate.sh`) runs alongside the coverage gate; both live under `make push-check`. A separate `make push-check-full` adds `test-integration` + `smoke-bundle` for pre-release checks (T-103).
-- **Amendment (2026-05-18):** "Ratchet up only" is the default but not absolute. A downward floor change is allowed iff *all three* hold: (a) the commit body explains the drop in one or two sentences (what added uncovered lines and why they're hard to test); (b) a follow-up ticket is filed in the same commit linking the gap to a fix; (c) the new floor is rounded down to the nearest whole percent of current actual coverage, so the drop stays small and the next commit that adds tests bumps it right back. Used sparingly — this exists for cases where new feature code lands behind a test-framework limitation (e.g. T-122's pumpWidget hang on a non-empty recents list), not for "we'll add tests later."
 - **Decision:** The pre-push gate runs `flutter test --coverage --exclude-tags forkpty`, parses `coverage/lcov.info`, and hard-fails if total line coverage drops below a committed floor at `coverage/floor.txt`. The floor starts at the actual current coverage (≈35%, dragged down by `lib/src/terminal/`'s 0.4%) and only ever ratchets up. The end target is 95%; getting there is tracked as a campaign of deliberate floor bumps under one epic ticket. **No carve-outs** — code under `lib/` is owned regardless of file-header attribution, including the terminal emulator port. Branch coverage is not gated (Dart's lcov output models it weakly). Lint suppressions to dodge the gate are never acceptable.
 - **Rationale:** A flat 95% threshold today blocks every push; an informational coverage report rots into noise. The committed-floor ratchet makes "don't make it worse" the durable rule and turns the journey to 95% into explicit, reviewed bumps rather than a single overnight cliff. Excluding `forkpty`-tagged tests matches `ci/test.sh` (forkpty + flutter test runner are incompatible — see `test/pty/session_test.dart`).
 - **Cost:** Pre-push wall time grows by `flutter test --coverage` (currently ≈11 s on this tree). Acceptable within D-29's < 90 s budget; reassess if it slips. Floor bumps require an explicit edit to `coverage/floor.txt` in the same commit that adds tests — so contributors can't silently raise it.