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>

.pql/pql-plan.json

@@ -1,5 +1,5 @@
 {
-  "exported_at": "2026-04-26T11:09:45Z",
+  "exported_at": "2026-04-26T11:27:24Z",
   "decisions": [
     {
       "id": "D-1",