feat(personalization): OperatorProfileBoundEvent + bind-at-start + inject about context

Records operator profile as a snapshot event at session start (invariants #8/#9),
populates SessionState.boundProfile via reducer, and injects the about text as a
pinned L0 SYSTEM context entry in every stage. Gated by PersonalizationConfig.enabled.

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

@@ -17,3 +17,13 @@ data class SessionWorkspaceBoundEvent(
     val workspaceRoot: String,
     val allowedPaths: List<String>,
 ) : EventPayload
+
+@Serializable
+@SerialName("OperatorProfileBound")
+data class OperatorProfileBoundEvent(
+    val sessionId: SessionId,
+    val about: String,
+    val approvalMode: String,
+    val preferredModels: List<String>,
+    val conventions: List<String>,
+) : EventPayload

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

@@ -10,6 +10,7 @@ import com.correx.core.events.events.ArtifactValidatingEvent
 import com.correx.core.events.events.ChatSessionStartedEvent
 import com.correx.core.events.events.ChatTurnEvent
 import com.correx.core.events.events.RouterNarrationEvent
+import com.correx.core.events.events.OperatorProfileBoundEvent
 import com.correx.core.events.events.SessionWorkspaceBoundEvent
 import com.correx.core.events.events.ContextTruncatedEvent
 import com.correx.core.events.events.EventPayload
@@ -91,6 +92,7 @@ val eventModule = SerializersModule {
         subclass(ChatTurnEvent::class)
         subclass(RouterNarrationEvent::class)
         subclass(SessionWorkspaceBoundEvent::class)
+        subclass(OperatorProfileBoundEvent::class)
         subclass(L3MemoryRetrievedEvent::class)
         subclass(ContextTruncatedEvent::class)
         subclass(ExecutionPlanLockedEvent::class)

core/events/src/test/kotlin/com/correx/core/events/serialization/OperatorProfileBoundEventSerializationTest.kt

@@ -0,0 +1,56 @@
+package com.correx.core.events.serialization
+
+import com.correx.core.events.events.EventPayload
+import com.correx.core.events.events.OperatorProfileBoundEvent
+import com.correx.core.events.types.SessionId
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class OperatorProfileBoundEventSerializationTest {
+
+    private val sample = OperatorProfileBoundEvent(
+        sessionId = SessionId("sess-1"),
+        about = "A seasoned backend engineer who prefers concise, idiomatic Kotlin.",
+        approvalMode = "auto",
+        preferredModels = listOf("llama-3-70b", "qwen2.5-72b"),
+        conventions = listOf("no var", "no mutable state"),
+    )
+
+    @Test
+    fun `round-trips as polymorphic EventPayload`() {
+        val encoded = eventJson.encodeToString(EventPayload.serializer(), sample)
+        assertTrue(encoded.contains("\"type\":\"OperatorProfileBound\""), "SerialName must be present: $encoded")
+        val decoded = eventJson.decodeFromString(EventPayload.serializer(), encoded)
+        assertEquals(sample, decoded)
+    }
+
+    @Test
+    fun `decodes hand-written OperatorProfileBound JSON`() {
+        val json = """
+            {"type":"OperatorProfileBound","sessionId":"s-99","about":"senior dev","approvalMode":"suggest","preferredModels":["model-a"],"conventions":["no null"]}
+        """.trimIndent()
+        val decoded = eventJson.decodeFromString(EventPayload.serializer(), json)
+        assertTrue(decoded is OperatorProfileBoundEvent)
+        decoded as OperatorProfileBoundEvent
+        assertEquals("s-99", decoded.sessionId.value)
+        assertEquals("senior dev", decoded.about)
+        assertEquals("suggest", decoded.approvalMode)
+        assertEquals(listOf("model-a"), decoded.preferredModels)
+        assertEquals(listOf("no null"), decoded.conventions)
+    }
+
+    @Test
+    fun `round-trips with empty lists`() {
+        val empty = OperatorProfileBoundEvent(
+            sessionId = SessionId("s-0"),
+            about = "",
+            approvalMode = "",
+            preferredModels = emptyList(),
+            conventions = emptyList(),
+        )
+        val encoded = eventJson.encodeToString(EventPayload.serializer(), empty)
+        val decoded = eventJson.decodeFromString(EventPayload.serializer(), encoded)
+        assertEquals(empty, decoded)
+    }
+}