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/agents/python-coder.md

@@ -154,7 +154,7 @@ request:
 ## Execution Rules
 - Run verification when needed using guarded bash commands.
 - Python verification path: `cd backend && source .venv/bin/activate && python -m pytest -v`
-- Python linting path: `cd backend && source .venv/bin/activate && python -m ruff check src/ tests/`
+- Python linting path: `cd backend && source .venv/bin/activate && python -m ruff check .`
 - Never bypass semantic debt to make code appear working.
 - Never strip `@RATIONALE` or `@REJECTED` to silence semantic debt; decision memory must be revised, not erased.
 - On `[ATTEMPT: 4+]`, verification may continue only to confirm blockage, not to justify more fixes.