fix(tui): slash.exec _pending_input commands, tool ANSI, terminal title

Additional TUI fixes discovered in the same audit:

1. /plan slash command was silently lost — process_command() queues the
   plan skill invocation onto _pending_input which nobody reads in the
   slash worker subprocess.  Now intercepted in slash.exec and routed
   through command.dispatch with a new 'send' dispatch type.

   Same interception added for /retry, /queue, /steer as safety nets
   (these already have correct TUI-local handlers in core.ts, but the
   server-side guard prevents regressions if the local handler is
   bypassed).

2. Tool results were stripping ANSI escape codes — the messageLine
   component used stripAnsi() + plain <Text> for tool role messages,
   losing all color/styling from terminal, search_files, etc.  Now
   uses <Ansi> component (already imported) when ANSI is detected.

3. Terminal tab title now shows model + busy status via useTerminalTitle
   hook from @hermes/ink (was never used).  Users can identify Hermes
   tabs and see at a glance whether the agent is busy or ready.

4. Added 'send' variant to CommandDispatchResponse type + asCommandDispatch
   parser + createSlashHandler handler for commands that need to inject
   a message into the conversation (plan, queue fallback, steer fallback).

ui-tui/src/lib/rpc.ts

@@ -26,6 +26,10 @@ export const asCommandDispatch = (value: unknown): CommandDispatchResponse | nul
     return { type: 'skill', name: o.name, message: typeof o.message === 'string' ? o.message : undefined }
   }
 
+  if (t === 'send' && typeof o.message === 'string') {
+    return { type: 'send', message: o.message }
+  }
+
   return null
 }