refactor(approval): wire ApprovalCoordinator end-to-end

ApprovalCoordinator (added in epic-13) was never instantiated. Its four
capabilities — multi-client fan-out, single-resolver dedupe, request
timeout, and a unified domain mapper — were duplicated piecemeal across
GlobalStreamHandler and SessionStreamHandler, with a STEER-outcome
divergence between them (coordinator mapped STEER → APPROVED while
GlobalStreamHandler mapped STEER → REJECTED). This refactor wires the
coordinator and removes the duplication.

Protocol: drop ApprovalDecision.STEER. STEER is no longer a discriminator;
it's expressed as (APPROVE | REJECT) + non-null steeringNote, so the user
can steer alongside either choice. TUI's current single-keybind STEER
input flow now sends APPROVE + note (matching the original epic-13
intent); a future overlay UX will let the user pick APPROVE or REJECT
explicitly.

Mapper: ClientMessage.ApprovalResponse → DomainApprovalDecision lives in
a single shared `toDomain` helper (apps/server/approval/
ApprovalResponseMapper.kt). Both stream handlers and the coordinator
use it.

Config: delete the duplicate apps/server/approval/ApprovalConfig.kt;
ApprovalCoordinator now takes core.config.ApprovalConfig (already had
timeoutMs=300_000L). ConfigLoader already populates it.

Wiring:
- ServerModule owns a SupervisorJob-backed moduleScope, constructs
  ApprovalCoordinator, and on start() subscribes eventStore.subscribeAll()
  to route ApprovalRequestedEvent payloads to onApprovalRequested.
- GlobalStreamHandler delegates ApprovalResponse to
  approvalCoordinator.handleResponse and registers/unregisters via the
  new registerGlobalClient/unregisterGlobalClient (global sockets aren't
  bound to one SessionId, so broadcasts union session and global sets).
- SessionStreamHandler delegates ApprovalResponse and registers per-session
  via registerClient/unregisterClient.
- Timeout is on by default at 5 minutes via config.timeoutMs.

Tests: ApprovalCoordinatorWiringTest covers delegate path, dedupe
producing ProtocolError, and event-stream subscription routing.

apps/tui/src/main/kotlin/com/correx/apps/tui/reducer/InputReducer.kt

@@ -69,7 +69,7 @@ object InputReducer {
                         Effect.SendWs(
                             ClientMessage.ApprovalResponse(
                                 requestId = ApprovalRequestId(active.requestId),
-                                decision = ApprovalDecision.STEER,
+                                decision = ApprovalDecision.APPROVE,
                                 steeringNote = text,
                             ),
                         ),

apps/tui/src/test/kotlin/com/correx/apps/tui/reducer/InputReducerTest.kt

@@ -132,7 +132,7 @@ class InputReducerTest {
     }
 
     @Test
-    fun `SubmitInput in STEER mode with active approval emits ApprovalResponse STEER`() {
+    fun `SubmitInput in STEER mode with active approval emits ApprovalResponse APPROVE with steering note`() {
         val (state, effects) = reduce(
             state = stateWithActiveApproval(inputMode = InputMode.STEER, inputBuffer = "steer this way"),
             action = Action.SubmitInput,
@@ -141,7 +141,7 @@ class InputReducerTest {
         assertEquals(1, effects.size)
         val effect = effects[0] as Effect.SendWs
         val msg = effect.message as ClientMessage.ApprovalResponse
-        assertEquals(ApprovalDecision.STEER, msg.decision)
+        assertEquals(ApprovalDecision.APPROVE, msg.decision)
         assertEquals("steer this way", msg.steeringNote)
         assertEquals("req-1", msg.requestId.value)
     }
@@ -155,7 +155,7 @@ class InputReducerTest {
         assertEquals(null, state.sessions.sessions[0].pendingApproval)
         assertEquals(1, effects.size)
         val msg = (effects[0] as Effect.SendWs).message as ClientMessage.ApprovalResponse
-        assertEquals(ApprovalDecision.STEER, msg.decision)
+        assertEquals(ApprovalDecision.APPROVE, msg.decision)
         assertEquals("go left", msg.steeringNote)
         assertEquals("req-1", msg.requestId.value)
     }

apps/tui/src/test/kotlin/com/correx/apps/tui/ws/ApprovalResponseGlobalSocketRoundTripTest.kt

@@ -46,14 +46,14 @@ class ApprovalResponseGlobalSocketRoundTripTest {
     fun `ApprovalResponse with steering note round-trips`() {
         val original: ClientMessage = ClientMessage.ApprovalResponse(
             requestId = ApprovalRequestId("req-steer"),
-            decision = ApprovalDecision.STEER,
+            decision = ApprovalDecision.APPROVE,
             steeringNote = "please retry with smaller batch",
         )
 
         val wire = clientJson.encodeToString(original)
         val decoded = ProtocolSerializer.decodeClientMessage(wire) as ClientMessage.ApprovalResponse
 
-        assertEquals(ApprovalDecision.STEER, decoded.decision)
+        assertEquals(ApprovalDecision.APPROVE, decoded.decision)
         assertEquals("please retry with smaller batch", decoded.steeringNote)
     }
 }