fix CI scripts referencing nonexistent app/ subdirectory

All six test/build scripts assumed a nested app/ package that
doesn't exist — the Flutter package lives at the repo root.
Removed every `cd app` and phantom path, consolidated the
redundant dart/flutter analyze passes in test.sh, and scoped
test_core.sh to core subsystem dirs so it no longer overlaps
with the full flutter test run.

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

ci/test_coverage.sh

@@ -6,12 +6,9 @@ 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.
+flutter test --coverage
 
 if command -v lcov >/dev/null 2>&1; then
   echo "==> lcov summary"
-  lcov --summary app/coverage/lcov.info
+  lcov --summary coverage/lcov.info
 fi