feat(kernel,events): freestyle graph re-routing — deterministic override core

Implements the replay-safe half of preemptive redirect (graph re-routing). An
operator-confirmed PreemptRedirectEvent overrides the resolver's edge at the next
transition boundary; the pure resolver stays untouched.

- PreemptRedirectEvent / PreemptRedirectBlockedEvent (+ serialization registration)
- TransitionExecutedEvent + TransitionDecision.Move gain optional redirectId — the
  durable 'consumed once' marker
- PreemptRedirect.decide: pure decision over the event log (override / block / none),
  so replay reaches the identical outcome without re-classifying (invariant #8)
- override wired in DefaultSessionOrchestrator.step above resolveTransition; back-edge
  jumps count against the existing maxRetries cap via executeMove
- blocks jumps to unknown stages or targets with unsatisfied needs
- DomainEventMapper: redirect events mapped to null (operator surface ships with the
  LLM-proposal + approval-confirm front-half)
- tests: override+consume-once, block-on-needs, block-on-unknown, ignore-consumed

Front-half (LLM proposal -> approval-gate confirm -> emit PreemptRedirectEvent) is
deferred; needs live LLM verification. Until it ships no redirect event is emitted in
production, so the override is inert. Spec: docs/plans/2026-06-10-freestyle-graph-rerouting.md

core/transitions/src/main/kotlin/com/correx/core/transitions/resolution/TransitionDecision.kt

@@ -7,7 +7,11 @@ sealed interface TransitionDecision {
 
     data class Move(
         val transitionId: TransitionId,
-        val to: StageId
+        val to: StageId,
+        // Set only when this Move was produced by a kernel-level preemptive redirect override
+        // (freestyle graph re-routing). The pure resolver never sets it; it threads to
+        // TransitionExecutedEvent.redirectId as the "redirect consumed" marker.
+        val redirectId: String? = null,
     ) : TransitionDecision
 
     data object Stay : TransitionDecision