fix(tui): release the adapter-registration listener on channel detach

Review follow-up: the llm/adapters-updated listener's disposer was
discarded, leaving it firing (harmlessly, behind isDisposed()) between
TUI shutdown and fiber disposal, asymmetric with the sibling channel
listeners. The controller now exposes detach(), and the channel's
detachListeners() calls it on both the dispose() and startup-failure
paths.

packages/ui/tui/src/index.ts

@@ -1563,6 +1563,7 @@ export function createTuiChat(
     disposeAgent()
     disposeSchemeListener()
     disposeTargetListeners()
+    modelController.detach()
   }
 
   // Sweep reveal of the whole banner: the header wipes in left-to-right over