New reusable pending-execution coordinator with fail-closed command matching:
- Store/TakeCatchUp/TakeRebuild/Cancel/Has/Peek
- TakeCatchUp: fail-closed on target LSN mismatch (cancel + return nil)
- TakeRebuild: same fail-closed semantics
- Cancel callback invoked on mismatch or explicit cancellation
9 tests prove boundary behavior:
- match succeeds, mismatch cancels, explicit cancel, noop on empty,
peek non-destructive, store replaces, take from empty
No weed/ imports. Pure coordination logic reusable by any adapter shell.
weed/server/block_recovery.go rebinding deferred to Task I.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>