fix: preserve switch intent when ExitCodeError is caught in local launcher

[easyfan]

Problem

Fixes #941.

When the user sends a message from the mobile app while in local (PTY) mode, doSwitch() is called which:

1. Sets exitReason = { type: 'switch' }
2. Sends SIGTERM to the claude PTY process via abort()

The PTY process exits with code 143 (SIGTERM), throwing an ExitCodeError. The catch block was unconditionally overwriting exitReason with { type: 'exit', code: 143 }, so instead of transitioning to remote mode, the entire process terminated.

Fix

Guard the ExitCodeError handler: if exitReason is already set (meaning doSwitch or doAbort already handled the intent), break without overwriting. The SIGTERM exit code in this case is expected — it's the result of us sending the signal ourselves.

 if (e instanceof ExitCodeError) {
+    if (exitReason) {
+        break; // preserve existing exit reason (e.g. switch intent) — SIGTERM is expected
+    }
     session.client.closeClaudeSessionTurn('failed');
     exitReason = { type: 'exit', code: e.exitCode };
     break;
 }

Testing

Reproduced by running happy locally, sending a message from the iOS app, and observing the process terminate instead of switching to remote mode. With this fix applied, the transition to remote mode completes correctly.

Diagnosed and fixed with Claude Code via Happy.

[bra1nDump]

Nice catch, merging — thanks @easyfan!

if you ever have 15 min to show us how you use Happy (or what's annoying), would really help us figure out what to build next: https://calendar.app.google/pozvqGvveyKpVUFh9