fix: keep TrackPath watches after atomic replacement

[Boulea7]

On Linux, TrackPath could lose a nested file after an atomic replacement when an ancestor already had an inotify handle. The parent was registered with the file-only optimization flag, so its handle could be skipped. The same path also left the stored mode as NoTrack when upgrading an existing watch.

This registers the parent as a directory and persists watch-mode upgrades. The regression tests cover both a direct TrackPath watch and a NoTrack → TrackPath upgrade, then verify that a normal write after replacement is still reported. This was isolated from vitejs/vite#23227.

Validation:

• new regression tests repeated 20 times
• Rust 1.90 MSRV test
• related TrackPath, NoTrack, recursive-upgrade, and unwatch tests
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo fmt --all -- --check
• workspace tests excluding six inotify exact-order failures reproduced on the base revision; two poll rename tests also failed intermittently only during concurrent workspace runs

AI-assisted tooling was used while implementing and testing this change; I reviewed the code and verification results.

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