GraphReFly storage tier dispatch + Node-side persistence.
Implements the G.27 storage tier protocol: tiered N-way storage with
per-tier transactions, debouncing, compaction, and codec
parameterization. Phase 13.6's deferred ACID atomicity tightening
lands here via redb, which provides
pure-Rust ACID transactions without a C dependency.
Status
M4 complete: tier dispatch, WAL, codecs, memory + file backends,
attach_storage reactive flush driver, durability/error/rollback
contracts (D268–D270). See docs/migration-status.md and
docs/porting-deferred.md for remaining storage follow-ons.
Key modules: [wal], [tier], [memory], [file] (feature file),
[redb] (feature redb-store), [graph_integration] (snapshot attach /
restore — consumed from graphrefly-graph).