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.plan.md

@@ -123,7 +123,8 @@ If a planned contract depends on unknown schema, relation target, or ADR identit
 Generate `quickstart.md` using real repository verification paths:
 - Backend: `cd backend && source .venv/bin/activate && python -m pytest -v`
 - Frontend: `cd frontend && npm run test`
-- Lint: `python -m ruff check backend/src/ backend/tests/`
+- Lint: `cd backend && python -m ruff check .`
+- Frontend lint: `cd frontend && npm run lint`
 - Docker: `docker compose up --build`
 
 ## Key Rules