fix: drop onMessage/onTyping frames that lack fields.args

[arbazkhan971]

Summary

onMessage and onTyping destructured fields.args with no guard. A changed frame without fields, or with fields but no args, threw a TypeError on the emit path.

Both handlers now drop that frame and log it at error instead of throwing. Existing well-formed frames still call back as before.

Test plan

• Existing well-formed onMessage / onTyping tests still pass
• New tests assert a missing fields.args does not throw and does not call the callback
• npx tsc --noEmit
• npm run lint

Fixes #378

Made with Cursor

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