Draft changelog: streaming latency and webhook auth updates

[mintlify]

Summary

Adds a Sep 8, 2026 changelog entry covering user-facing changes shipped since the Sep 1 entry.

Changes

• Faster streaming delivery: P99 latency improved from ~6-7s to ~4-5s across streaming endpoints.
• Webhook management endpoints now accept OAuth 2.0 user-context authentication.
• X Activity API update/delete subscription endpoints now accept OAuth 2.0 user-context and OAuth 1.0a authentication.

Context

Sourced from merges to main since the last changelog entry: the streaming latency docs update and OpenAPI spec syncs that expanded accepted auth methods on webhook and activity subscription endpoints.

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Project	Status	Preview	Updated
x-corp	🟢 Ready	View Preview	Sep 8, 2026, 8:11 PM

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