* feat: replace pure-JS xxHash32 with native Rust implementation via napi
The hashline edit tool calls xxHash32 on every line of every file read/edit.
Moving this to a native Rust implementation (xxhash-rust crate) eliminates
JS overhead for this hot path. Hash output is identical -- verified by tests
comparing native vs JS reference across 11 input vectors including empty
strings, short/long inputs, unicode, and seeded variants.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
* fix: use typed native interface and remove version-drag comment in xxhash wrapper
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>