Indexing: cancel parses on a budget instead of kill-and-retry (deterministic timeouts cost 3 x 30s + a dropped file) #20

Found in the PR #18 review (F3, altitude).

A parse that times out is retried twice (parse-pool.ts: 10s base, 3x hard kill; then a retry, then a comments-stripped retry). A deterministic livelock therefore costs about 90s per file, and the file is still dropped.

src/extraction/parse-budget.ts already cancels wasm parses through progressCallback. Using it for indexing parses, and not retrying a parse that hit its budget, would turn any future error-recovery livelock, in any grammar or runtime, into one bounded failure instead of three worker kills. The kernel would need an equivalent progress callback (see the kernel livelock issue).