Draft changelog: Broadcast chat removal events

[mintlify]

Summary

Tightens the Sep 29, 2026 changelog entry for the new broadcast.chat.remove X Activity API event.

Changes

• Switched to skimmable bullets (scope, payload, Livestream delete trigger)
• Replaced full-URL internal link with a root-relative path
• Added links to Delete chat message and Accessing live chat step 4

Context

Only change since the previous changelog entry is #471.

[mintlify]

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Project	Status	Preview	Updated
x-corp	🟢 Ready	View Preview	Sep 29, 2026, 6:30 PM

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