## Implementation Plan: Fix Playwright Async Context Manager Race in DeepSearch

### Summary

Add a module-level `asyncio.Lock()` in `devplacepy/services/jobs/deepsearch/crawl.py` to serialize all calls to `_render_with_playwright`. This eliminates the race condition where two concurrently running `fetch_page` tasks attempt to enter the same `async with async_playwright() as pw:` context, which is not safe for concurrent access.

### Files to Change

1. **`devplacepy/services/jobs/deepsearch/crawl.py`** – single addition: module-level lock and its use inside `fetch_page`.

### Detailed Steps

1. Modify `devplacepy/services/jobs/deepsearch/crawl.py`:
   - **Import** `asyncio` if not already imported.
   - **Add at module scope** (after existing imports, before any function definitions):
     ```python
     _deepsearch_playwright_lock = asyncio.Lock()
     ```
   - **Inside `fetch_page` function**, located around lines 238–249 (the block that checks `if len(text) < MIN_PAGE_CHARS`):
     - Replace the line `r_title, r_text, r_status, r_links = await _render_with_playwright(url)` with:
       ```python
       async with _deepsearch_playwright_lock:
           r_title, r_text, r_status, r_links = await _render_with_playwright(url)
       ```
     - Preserve all adjacent logic unchanged.

2. Verify no other file needs changes. The lock only protects the Playwright session; the rest of the crawl pipeline (HTTPX fetches, result processing) remains fully concurrent.

### Testing & Verification

- The project’s test command and lint command must pass. Earlier attempts failed due to Python environment restrictions (PEP 668). To avoid that, **run all commands inside a virtual environment** or add `--break-system-packages` if safe and allowed. The plan below assumes a venv is active.

### Definition of Done

- [ ] The lock and its application have been added to `devplacepy/services/jobs/deepsearch/crawl.py` as described.
- [ ] Syntax check passes: `python3 -m py_compile devplacepy/services/jobs/deepsearch/crawl.py`
- [ ] Lint passes: `pip install -q ruff && ruff check devplacepy/services/jobs/deepsearch/crawl.py`
- [ ] Unit tests pass: `pip install -e '.[dev]' -q && make test-unit` (if `make test-unit` fails due to environment, use `python3 -m pytest tests/unit/ -x -q` instead)
- [ ] No other Playwright consumer in the codebase is affected (all remain unchanged).
- [ ] The fix is isolated: no changes to `pyproject.toml`, `CHANGELOG.md`, or test files unless instructed.