Bound the parser's memory on large repositories #48

Since #17, analyze parses TypeScript/JavaScript files with oxc-parser. Peak memory grows with the number of parsed files, because the parser frees native memory only after a garbage collection that nothing triggers. On angular/angular, peak RSS rises from about 170 MB to about 370–425 MB (default window) and to about 500 MB with --since 10y (docs/toolchain.md).

Forcing a GC through --expose-gc at runtime was measured and rejected; Node documents changing V8 flags after start as undefined behaviour.

Idea: parse in a worker thread (or a pool) that is recycled after N files, so the native memory is released with the worker.

Done when: peak RSS on angular/angular in the default window stays within about 1.5× the pre-#17 baseline, wall time does not regress, and docs/toolchain.md has the new numbers.