mod.rs was 937 lines with all Store methods in one block.
Split into three files by responsibility:
- persist.rs (318 lines): load, save, replay, append, snapshot
— all disk IO and cache management
- ops.rs (300 lines): upsert, delete, modify, mark_used/wrong,
decay, fix_categories, cap_degree — all mutations
- mod.rs (356 lines): re-exports, key resolution, ingestion,
rendering, search — read-only operations
No behavioral changes; cargo check + full smoke test pass.
