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/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)
+    }
 }