* Add native pHash deduplication acceleration

* Name candidate mark states in native dedup index.

Replace magic 0/1/2 literals with a documented CandidateMark enum so Hamming-index query state is easier to follow.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Address native dedup review nits

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Co-authored-by: Cursor <cursoragent@cursor.com>