Draft changelog: streaming latency and webhook auth updates

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Summary

Adds a Sep 7, 2026 changelog entry covering user-facing X API v2 changes shipped since the Sep 1 entry.

Changes

• Faster streaming delivery: P99 latency for hydrated streams (including Filtered Stream) improved from ~6-7 seconds to ~4-5 seconds.
• Webhook management endpoints and X Activity API subscription update/delete now accept OAuth 2.0 and OAuth 1.0a user-context authentication in addition to app-only Bearer tokens.

Context

Derived from changes merged to main since the last changelog entry. Docs-only edits (page regeneration, scope reordering, prose moves) were excluded.

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Project	Status	Preview	Updated
x-corp	🟢 Ready	View Preview	Sep 7, 2026, 2:16 AM

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