fix(sessions): terminalize session on workflow completion

DefaultSessionReducer skipped WorkflowCompletedEvent to avoid terminalizing on freestyle planning's mid-session completion, but that left execution/normal completions stuck ACTIVE forever — headless watchers and approval loops never saw a terminal state. Add workflowId to WorkflowCompletedEvent (defaulted for replay compat), pass graph.id at all completeWorkflow sites, and terminalize to COMPLETED unless it's the freestyle_planning handoff. Correct stale tests that pinned the ACTIVE-forever behavior.

core/events/src/main/kotlin/com/correx/core/events/events/OrchestrationEvents.kt

@@ -21,6 +21,10 @@ data class WorkflowCompletedEvent(
     val sessionId: SessionId,
     val terminalStageId: StageId,
     val totalStages: Int,
+    // The workflow that completed. Lets the session reducer tell a session-terminal completion from
+    // the freestyle planning workflow, which completes mid-session before handing off to execution.
+    // Defaulted for backward-compatible replay of events stored before this field existed.
+    val workflowId: String = "",
 ) : EventPayload
 
 @Serializable