RFC 0015: Epic / Tracking issue for FileMeta path normalization

[rmanibus]

Context

Track completion and rollout for RFC 0015 (FileMeta Path Normalization).

RFC: rfcs/0015-filemeta-path-normalization.md

Goal

Reduce filemeta/ object size and avoid unnecessary hash churn by removing path duplication from persisted FileMeta data while preserving restore and traversal behavior.

Scope

• FileMeta/schema updates and compatibility behavior.
• Backup/restore/HAMT traversal changes needed to reconstruct paths correctly.
• Migration and mixed-snapshot compatibility validation.
• Documentation and rollout notes.

Related RFCs

• RFC 0001
• RFC 0006

Exit criteria

• New snapshots no longer persist redundant path arrays in FileMeta where the RFC says they should not.
• Restore/listing behavior remains correct across old and new snapshot shapes.
• Compatibility and regression coverage exist for mixed repository history.