feat: wire ChatMode.STEERING toggle in TUI input bar

- Add ChatMode.STEERING toggle via ctrl+s keybinding
- Add KeyEvent.ToggleSteeringMode, Action.CycleChatMode
- TambouiKeyMapper: map ctrl+s to ToggleSteeringMode
- KeyResolver: route ToggleSteeringMode to CycleChatMode (global)
- InputReducer: toggle chatMode between CHAT and STEERING
- TuiState: add chatMode field (default CHAT)
- SessionsReducer: use ctx.chatMode instead of hardcoded CHAT
- RootReducer: pass afterInput.chatMode to SessionsReducerContext
- InputBar: show blue 'chat' or magenta 'steer' label in status line

Activation: ctrl+s toggles mode, 'steer' label appears, submitted
ChatInput uses ChatMode.STEERING → router emits SteeringNoteAddedEvent
→ context builder folds into next stage's context pack

core/kernel/src/main/kotlin/com/correx/core/kernel/orchestration/SessionOrchestrator.kt

@@ -549,16 +549,28 @@ abstract class SessionOrchestrator(
     private suspend fun buildSteeringNoteEntries(sessionId: SessionId): List<ContextEntry> {
         val events = eventStore.read(sessionId)
         return events.mapNotNull { event ->
-            (event.payload as? SteeringNoteAddedEvent)?.let { steering ->
-                ContextEntry(
+            when (val p = event.payload) {
+                is SteeringNoteAddedEvent -> ContextEntry(
                     id = ContextEntryId(UUID.randomUUID().toString()),
                     layer = ContextLayer.L2,
-                    content = steering.content,
+                    content = p.content,
                     sourceType = "steeringNote",
-                    sourceId = steering.stageId?.value ?: sessionId.value,
-                    tokenEstimate = estimateTokens(steering.content),
+                    sourceId = p.stageId?.value ?: sessionId.value,
+                    tokenEstimate = estimateTokens(p.content),
                     role = EntryRole.SYSTEM,
                 )
+                is ApprovalDecisionResolvedEvent -> p.userSteering?.let { steering ->
+                    ContextEntry(
+                        id = ContextEntryId(UUID.randomUUID().toString()),
+                        layer = ContextLayer.L2,
+                        content = steering.text,
+                        sourceType = "steeringNote",
+                        sourceId = steering.sessionId.value,
+                        tokenEstimate = estimateTokens(steering.text),
+                        role = EntryRole.USER,
+                    )
+                }
+                else -> null
             }
         }
     }