Draft changelog: weekly roundup for Aug 29

[mintlify]

Summary

Adds a weekly changelog entry covering user-facing X API changes shipped since the last entry (Aug 13).

Changes

• New features: broadcast.start/broadcast.end events in the X Activity API, filter.qualifiers on X Activity API subscriptions, and the GET /2/usage/credits endpoint for Pay-Per-Use credit balances.
• Updates: is_subscriber boolean added to the broadcast.chat event payload.
• Docs-only changes (navigation fixes, page fixes, customer directory update) were excluded.

Context

Based on PRs merged to xdevplatform/docs since Aug 13, 2026 (#324, #329, #340, #342).

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Project	Status	Preview	Updated (UTC)
x-corp	🟢 Ready	View Preview	Aug 29, 2026, 5:12 PM

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