Introduce an optional go-store persistence layer for the three state
groups described in RFC §15.3 — queue, concurrency, registry — plus
runtime_state and dispatch_history used by the sync pipeline.
- statestore.go lazily opens `.core/db.duckdb` via go-store when
available; nil-safe helpers return cleanly so in-memory/file-based
fallbacks survive when the store cannot open (graceful degradation,
RFC §15.6)
- prep.go tracks the store reference on the subsystem and closes it on
shutdown; hydrateWorkspaces now consults the registry group before
the filesystem scan so ghost agents are marked failed across
restarts, and TrackWorkspace mirrors updates back into the cache
- runtime_state.go persists backoff + fail-count snapshots into the
go-store runtime group so dispatch backoff survives restarts even
when the JSON file rotates
- commit.go writes the completed dispatch record into dispatch_history
for RFC §16.3 sync push to drain without rescanning workspaces
- statestore_test.go covers lazy-once init, restore/delete round trip,
ghost-agent failure marking, and runtime-state replay across
subsystem instances
Co-Authored-By: Virgil <virgil@lethean.io>
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