Eric Coissac
0733287de5
Refactor `PersistentCompactIntVecBuilder` to replace in-memory `Vec<u8>` with `MmapMut` for primary storage. Decouples initialization from finalization by updating `finalize_pciv` to truncate, append overflow data, and overwrite the header placeholder. Adds file path tracking via a new `path()` accessor, implements `build_from` for efficient copying, and introduces arithmetic/set operations (`min`, `max`, `sum`, `diff`). Expands test coverage for persistence roundtrips, mutations, iteration, and the new vector operations.
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