feat(FN-5256): merge fusion/fn-5256

docs/architecture.md

@@ -614,6 +614,7 @@ See [Memory Plugin Contract](./memory-plugin-contract.md) for the full plan.
 ### Scheduling and execution
 - `Scheduler` (`scheduler.ts`) — dependency-aware task scheduling that dispatches eligible todo tasks by priority first, then dependency-unblock fanout within the same priority class (FN-4969), then FIFO (`createdAt` ascending) with task-id fallback. `urgent` always stays ahead of lower priorities, and overlap/file-scope blockers are excluded from fanout weighting.
   - `blockedBy` invariant (FN-3924/FN-4091): the field is only durable when it references a current unresolved explicit dependency (or, for dependency-free tasks, an active overlap blocker). Completion gating now validates `blockedBy` through live task resolution: missing blockers and blockers already in `done`/`archived` are treated as stale, while only still-active blockers continue to prevent `fn_task_done`. If no current blocker remains, scheduler/event reconciliation clears `blockedBy` to `null` and re-evaluates from live task state.
+  - Dependency-cycle invariant (FN-5256): task dependency graphs are acyclic at write time (`DependencyCycleError` in `TaskStore` for `createTask`, `createTaskWithReservedId`, `updateTask`, and `applyReplicatedTaskCreate`) with `task:dependency-cycle-rejected` audit evidence. Self-healing batch 2 adds `reconcileDependencyCycles`, which emits `task:dependency-cycle-detected`, auto-repairs only bounded umbrella-back-edge loops via `task:auto-reconciled-dependency-cycle`, and leaves ambiguous cycles untouched with `task:dependency-cycle-unrepaired` for operator inspection.
 
 #### BlockedBy stamping invariants
 - Scheduler writes overlap-based `blockedBy` only when overlap gating is active and there is a live overlapping active scope; otherwise overlap logic does not stamp blockers.