fix: handle errors in streaming output callback to prevent group hangs

[cmraible-bot]

Summary

• The outputChain in container-runner.ts chains onOutput callbacks via .then() with no .catch() handler
• If onOutput throws (e.g. channel.sendMessage fails due to network error, invalid JID, rate limiting), the promise chain silently rejects
• The close handler uses outputChain.then(() => resolve(...)) — with a rejected chain, this .then() never fires, and runContainerAgent's promise hangs forever
• This permanently blocks all message processing for the affected group until the process is restarted
• Fix: Added .catch() to the output chain so errors are logged and the chain continues, ensuring the container-runner promise always settles

Why this matters

The synchronous try/catch around line 365 only catches JSON.parse() errors. onOutput is async (returns a Promise), so when it's scheduled via .then(), any errors it throws happen on a later microtask — outside the synchronous try/catch. Without .catch() on the promise chain, the rejection is unhandled and the close handler's outputChain.then(() => resolve(...)) never fires.

Test plan

• Added test: onOutput error does not hang the promise — verifies that when onOutput throws, the promise still resolves instead of hanging
• All existing tests still pass
• Typecheck passes
• Prettier formatting check passes

🤖 Generated with Claude Code

[TomGranot]

This looks solid — preventing group hangs from streaming errors is important. @gavrielc mind giving this a quick look? Should be a straightforward review.