feat(toolintent): record the session's active task as a session-local fact

Claiming a task now emits SessionWorkingTaskEvent{taskId, affectedPaths} into the
session's own stream (via a SessionFactRecorder port + event-store adapter), and
SessionContextProjection folds it into SessionContext.activeTask. So a gate learns
"which task is this session working, and its scope" by reading the session stream
— no cross-stream scan, no kernel->tasks dependency. Re-emitted on an affected_paths
edit by the claimant, so the snapshot scope stays current; latest wins on replay.

This is the data source the write-scope gate needs (next).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

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

@@ -1,6 +1,7 @@
 package com.correx.core.events.events
 
 import com.correx.core.events.types.SessionId
+import com.correx.core.events.types.TaskId
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
 
@@ -10,6 +11,20 @@ data class ChatSessionStartedEvent(
     val sessionId: SessionId,
 ) : EventPayload
 
+/**
+ * Records, in the session's own stream, that this run claimed [taskId] and is working it with the
+ * declared [affectedPaths] write scope — a session-local fact so the gates know the active task
+ * without scanning task streams. Re-emitted when the claimant edits affected_paths, so the folded
+ * scope stays current; SessionContextProjection takes the most recent.
+ */
+@Serializable
+@SerialName("SessionWorkingTask")
+data class SessionWorkingTaskEvent(
+    val sessionId: SessionId,
+    val taskId: TaskId,
+    val affectedPaths: List<String> = emptyList(),
+) : EventPayload
+
 @Serializable
 @SerialName("SessionWorkspaceBound")
 data class SessionWorkspaceBoundEvent(

core/events/src/main/kotlin/com/correx/core/events/serialization/Serialization.kt

@@ -12,6 +12,7 @@ import com.correx.core.events.events.ArtifactValidatingEvent
 import com.correx.core.events.events.BriefEchoMismatchEvent
 import com.correx.core.events.events.BriefGroundingCheckedEvent
 import com.correx.core.events.events.ChatSessionStartedEvent
+import com.correx.core.events.events.SessionWorkingTaskEvent
 import com.correx.core.events.events.ClarificationAnsweredEvent
 import com.correx.core.events.events.ClarificationRequestedEvent
 import com.correx.core.events.events.ChatTurnEvent
@@ -139,6 +140,7 @@ val eventModule = SerializersModule {
         subclass(BriefEchoMismatchEvent::class)
         subclass(RiskAssessedEvent::class)
         subclass(ChatSessionStartedEvent::class)
+        subclass(SessionWorkingTaskEvent::class)
         subclass(ChatTurnEvent::class)
         subclass(RouterNarrationEvent::class)
         subclass(SessionWorkspaceBoundEvent::class)

core/toolintent/src/main/kotlin/com/correx/core/toolintent/SessionContext.kt

@@ -1,5 +1,6 @@
 package com.correx.core.toolintent
 
+import com.correx.core.events.events.SessionWorkingTaskEvent
 import com.correx.core.events.events.StoredEvent
 import com.correx.core.events.events.ToolExecutionCompletedEvent
 import com.correx.core.events.events.ToolInvocationRequestedEvent
@@ -40,6 +41,12 @@ class SessionContextProjection(private val sessionId: SessionId) : Projection<Se
         when (val payload = event.payload) {
             is ToolInvocationRequestedEvent -> recordPendingRead(state, payload)
             is ToolExecutionCompletedEvent -> recordCompletion(state, payload)
+            is SessionWorkingTaskEvent ->
+                if (payload.sessionId == sessionId) {
+                    state.copy(activeTask = ActiveTask(payload.taskId.value, payload.affectedPaths))
+                } else {
+                    state
+                }
             else -> state
         }
 

core/toolintent/src/test/kotlin/com/correx/core/toolintent/SessionContextProjectionTest.kt

@@ -6,9 +6,11 @@ import com.correx.core.events.events.EventPayload
 import com.correx.core.events.events.StoredEvent
 import com.correx.core.events.events.ToolExecutionCompletedEvent
 import com.correx.core.events.events.ToolInvocationRequestedEvent
+import com.correx.core.events.events.SessionWorkingTaskEvent
 import com.correx.core.events.events.ToolReceipt
 import com.correx.core.events.events.ToolRequest
 import com.correx.core.events.types.EventId
+import com.correx.core.events.types.TaskId
 import com.correx.core.events.types.SessionId
 import com.correx.core.events.types.StageId
 import com.correx.core.events.types.ToolInvocationId
@@ -76,4 +78,16 @@ class SessionContextProjectionTest {
         assertEquals(setOf("core/A.kt", "core/B.kt"), ctx.writes)
         assertTrue(ctx.reads.isEmpty())
     }
+
+    @Test
+    fun `a SessionWorkingTask event sets the active task and the latest wins`() {
+        val ctx = fold(
+            listOf(
+                stored(SessionWorkingTaskEvent(session, TaskId("auth-1"), listOf("core/a/**"))),
+                stored(SessionWorkingTaskEvent(session, TaskId("auth-2"), listOf("core/auth/**"))),
+            ),
+        )
+        assertEquals("auth-2", ctx.activeTask?.taskId)
+        assertEquals(listOf("core/auth/**"), ctx.activeTask?.scope)
+    }
 }