Draft changelog: Sep 25, 2026 weekly updates

[mintlify]

Summary

Adds a Sep 25, 2026 changelog entry covering product changes shipped since the Sep 21 entry.

Changes

• New features: X Activity API subscription expires_at, OAuth 2.0 client secret webhook signing, is_moderator on broadcast.chat
• Updates: broadcast scopes in OAuth 1.0a token exchange, Chat join-request approval, Livestream API whitelist access form
• Bug fixes: batch compliance 128 MB upload limit, source removed from tweet.fields

Context

Sourced from PRs #441, #443, #445, #448, #450, #451, #454 and OpenAPI spec updates. Docs-only changes (e.g. #459) were excluded.

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Project	Status	Preview	Updated
x-corp	🟢 Ready	View Preview	Sep 25, 2026, 8:08 PM

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