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.

testing/projections/src/test/kotlin/DefaultSessionReducerTest.kt

@@ -75,7 +75,7 @@ class DefaultSessionReducerTest {
     }
 
     @Test
-    fun `WorkflowCompletedEvent leaves ACTIVE status`() {
+    fun `WorkflowCompletedEvent flips to COMPLETED status`() {
         val state = activeState()
 
         val result = reducer.reduce(
@@ -86,11 +86,11 @@ class DefaultSessionReducerTest {
             )
         )
 
-        assertEquals(SessionStatus.ACTIVE, result.status)
+        assertEquals(SessionStatus.COMPLETED, result.status)
     }
 
     @Test
-    fun `WorkflowFailedEvent leaves ACTIVE status`() {
+    fun `WorkflowFailedEvent flips to FAILED status`() {
         val state = activeState()
 
         val result = reducer.reduce(
@@ -101,7 +101,7 @@ class DefaultSessionReducerTest {
             )
         )
 
-        assertEquals(SessionStatus.ACTIVE, result.status)
+        assertEquals(SessionStatus.FAILED, result.status)
     }
 
     @Test

testing/projections/src/test/kotlin/SessionProjectorTest.kt

@@ -35,7 +35,7 @@ class SessionProjectorTest {
             state = projector.apply(state, it)
         }
 
-        assertEquals(SessionStatus.CREATED, state.status)
+        assertEquals(SessionStatus.COMPLETED, state.status)
     }
 
     @Test