fix(codegraph): clean up watcher and worker pool on init failure

[ardelperal]

Summary

• ensure CodeGraph.close() and ParseWorkerPool.destroy() always run on init/index failure
• move close logic into a finally block and destroy the worker pool before re-throwing
• extend watchdog coverage for Windows real disposable worktree cleanup

Validation

• 5 focused tests pass, 1 POSIX-only test skipped on Windows
• TypeScript typecheck passed
• real disposable Windows worktree cleanup verified
• native bounded review lineage review-8039f5997b0ec7e8 entered native_stop after refuter; delivery proceeds under ordinary repository policy

Closes #241