Draft changelog: Activity API events, qualifiers, usage credits

[mintlify]

Summary

Adds a weekly changelog entry (Aug 30, 2026) covering product changes shipped since the last entry on Aug 13.

Changes

• New features: broadcast.start/broadcast.end events and filter.qualifiers for X Activity API subscriptions, and the new GET /2/usage/credits endpoint for PPU credit balance
• Updates: is_subscriber field on broadcast.chat payloads, and Pay-per-use monthly Post read cap raised from 2M to 3M

Context

Reviewed all 12 PRs merged since Aug 13. Docs-only fixes (navigation, broken links, stale page references) were excluded as they are not product changes.

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Project	Status	Preview	Updated (UTC)
x-corp	🟢 Ready	View Preview	Aug 30, 2026, 5:10 PM

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