fix(lint): apply QA-found gaps in agent instruction files

- python-coder.md: ruff check src/ tests/ → ruff check .
- speckit.test.md: add frontend npm run lint
- speckit.plan.md: ruff check . + frontend lint
- speckit.tasks.md: ruff check . + frontend lint
- fullstack-coder.md: move npm run lint to frontend block

.opencode/command/speckit.tasks.md

@@ -100,7 +100,8 @@ Each story phase must end with:
 
 Typical verification tasks may include:
 - `cd backend && source .venv/bin/activate && python -m pytest backend/tests/test_*.py -v`
-- `python -m ruff check backend/src/ backend/tests/`
+- `cd backend && python -m ruff check .`
+- `cd frontend && npm run lint`
 - `cd frontend && npm run test`
 - `cd frontend && npm run build`