fix password fields not clearing after validation error

When pasting an invalid token, the old value stayed in the input
field. Pasting a new token appended to the old one instead of
replacing it, causing repeated validation failures.

Add clearOnError: true to all 8 password prompts across setup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

setup/channels/imessage.ts

@@ -250,6 +250,7 @@ async function collectRemoteCreds(): Promise<RemoteCreds> {
   const keyAnswer = ensureAnswer(
     await p.password({
       message: 'Photon API key',
+      clearOnError: true,
       validate: (v) => ((v ?? '').trim() ? undefined : 'API key is required'),
     }),
   );