Update CHAIN_OF_THOUGHTS.md

[compulim]

Add the missing "activity.type" field

Changelog Entry

(No changelog entry for updating docs.)

Description

The activity payload has missing type field, it should be "message" (or "typing" for livestreaming.)

Design

Specific Changes

• Update docs/CHAIN_OF_THOUGHTS.md

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)