perf: compare cached path hash before path

[hardfist]

Summary

• Compare CachedPath memoized hashes before falling back to path equality.
• Compare dyn CacheKey memoized hashes before falling back to path equality, covering borrowed cache lookup paths like DashSet::get((hash, path).borrow()).
• Keep path comparison as the collision guard.

Test

• rustfmt --edition 2021 src/cache.rs
• cargo test --no-run using installed nightly-aarch64-apple-darwin because local pinned nightly-2025-11-10 is incomplete
• cargo test tests::simple::simple
• Full cargo test was not rerun for this follow-up; previous full run failed in existing PnP fixture resolution cases with NotFound(...) errors

[codspeed-hq]

Merging this PR will not alter performance

✅ 12 untouched benchmarks

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_{Comparing perf/cached-path-eq-hash (fa0ba02) with main (31610e6)}