fix(#240): notification tap race condition opens new chat instead of correct session (#241)

Two-pronged fix for the race between GatewayReady auto-creating a session
and ChatScreen LaunchedEffect calling switchSession:

1. ChatViewModel: added `initialSessionId` field. GatewayReady now checks
   this before auto-creating a session — if set, it calls switchSession
   instead. The field is set synchronously by ChatScreen via SideEffect
   during composition, before any WS event can be processed.

2. ChatScreen: LaunchedEffect now keys on state.connectionStatus and
   waits for CONNECTED before calling switchSession. This prevents the
   SESSION_RESUME message from being dropped (webSocket is null before
   onOpen, so send() is a silent no-op).

Fixes #240

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/test/java/com/m57/hermescontrol/ui/chat/ChatViewModelTest.kt

@@ -128,6 +128,36 @@ class ChatViewModelTest {
             verify { HermesWsClient.send(WsMethods.SESSION_CREATE, any(), any()) }
         }
 
+    @Test
+    fun testGatewayReady_withInitialSessionId_switchesToIt() =
+        runTest {
+            val viewModel = ChatViewModel(app, startCleanup = false)
+            advanceUntilIdle()
+
+            // Set the initial session ID (normally done by ChatScreen SideEffect)
+            viewModel.initialSessionId = "session-from-notification"
+            mockConnectionStatus.value = ConnectionStatus.CONNECTED
+            mockEventsFlow.emit(WsEvent.GatewayReady(null))
+            advanceUntilIdle()
+
+            val state = viewModel.uiState.value
+            assertTrue(state.isConnected)
+            // Should NOT have called createNewSession — switchSession was used instead
+            assertEquals("session-from-notification", state.currentSessionId)
+
+            // Verify SESSION_RESUME was sent instead of SESSION_CREATE
+            verify { HermesWsClient.send(WsMethods.SESSION_LIST, any(), any()) }
+            verify {
+                HermesWsClient.send(
+                    WsMethods.SESSION_RESUME,
+                    mapOf("session_id" to "session-from-notification"),
+                    any(),
+                )
+            }
+            // SESSION_CREATE must NOT be sent
+            verify(inverse = true) { HermesWsClient.send(WsMethods.SESSION_CREATE, any(), any()) }
+        }
+
     @Test
     fun testSessionCreateRpcResult() =
         runTest {