add Makefile test-layer targets + rename coverage.sh

Makefile grows targets for each test layer (test, test-a11y,
test-integration, test-e2e, test-all), the coverage + smoke-bundle
helpers, and the UI harness (ui-dev, ui-stop, ui-smoke). push-check
now runs `test + test-a11y` — fast pre-push gate under 90s.

ci/coverage.sh is renamed to ci/test_coverage.sh so it matches the
`test_*.sh` naming of the other layer scripts and sidesteps the
repo's `coverage.*` gitignore pattern (intended for coverage output
files like coverage.lcov, not scripts).

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

ci/test_coverage.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# Generate + summarize lcov coverage. No thresholds yet (see plan's
+# "Open questions deferred" — we let the suite run for a week of real
+# commits before setting hard gates that would just need tuning).
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+echo "==> flutter test --coverage"
+(cd app && flutter test --coverage)
+
+echo "==> root dart coverage (skipped until dart_test + coverage integrate)"
+# dart test doesn't emit lcov natively; wire package:coverage later.
+
+if command -v lcov >/dev/null 2>&1; then
+  echo "==> lcov summary"
+  lcov --summary app/coverage/lcov.info
+fi