Mocks chokidar at the module level for `__tests__/watcher.test.ts` and
`__tests__/mcp-staleness-banner.test.ts` so the pending-file-tracking and
staleness-banner tests no longer depend on OS-level file-watcher delivery
latency. Reduces full-suite failure rate from 3/10 to 0/10.
- `__tests__/__helpers__/chokidar-mock.ts` (new) — controllable
EventEmitter; `chokidarMockModule` for `vi.mock('chokidar', ...)` plus
`triggerFileEvent(root, event, relPath)` helper. `watch()` returns an
EventEmitter that fires `ready` on the next microtask.
- `__tests__/watcher.test.ts` — refactors every event-driving test to
use `triggerFileEvent` instead of `fs.writeFileSync` for the trigger.
Pending-file tests assert state synchronously. Filtering tests still
verify FileWatcher's own filter chain.
- `__tests__/mcp-staleness-banner.test.ts` — same vi.mock + same
`triggerFileEvent` pattern; tests keep `fs.writeFileSync` for on-disk
content (`cg.sync()` needs the bytes) and add the synthesized event
on top.
The watcher's debounce timer (real `setTimeout`) is left untouched — that's
the unit under test.
Total test count unchanged (928 passing + 2 pre-existing skips). Wall-clock
runtime improved (no more 8000ms waitFor polls against real chokidar).
One disclosed tradeoff: the previous node_modules filtering test
incidentally exercised chokidar's `ignored` callback at the OS level;
with chokidar mocked, that property of chokidar itself isn't covered
here. Commented inline.
