🚀 v0.8.9 - #918

Summary

I prepared the v0.8.9 release notes and corrected persistent configuration and upgrade docs against LibreChat dev at 40671fd88c.

• Add concise release highlights and link the RC1 notes and Config v1.3.18 guidance.
• Attribute all 349 merged PRs and both direct commits through LibreChat dev at 40671fd88c.
• Highlight opt-in Slack Agents and background Responses, Tool Search, BYOM, new models, and conversation recovery.
• State Slack gateway/storage requirements and restricted GPT-6 Cyber access.
• Include the intended RC1-to-v0.8.9 comparison link.
• Document post-RC1 config changes separately from the immutable published Config v1.3.18 notes.
• Document PostgreSQL favorites migration/cutover, spreadsheet parsing limits, permission lookup budgets, file cleanup, STT MIME routing, and model-spec tool deferral.
• Correct password-reset email requirements, deployment-owned override precedence, telemetry identity, and restricted model availability.

Slack and background Responses feature pages remain owned by PR #892, which is a release-doc dependency. This PR does not duplicate those pages. Before publication, verify that #892 distinguishes foreground approval handling from background owner review, documents explicit foreground store: true, and includes the shared-workspace deployment opt-in behavior.

The app's config constant is still 1.3.18. This docs PR records the additions without assigning a config version that has not been bumped in the app.

Change Type

• Documentation update

Testing

• Ran targeted Prettier against all changed MDX pages.
• Ran fumadocs-mdx and tsc --noEmit.
• Ran the release changelog coverage audit against v0.8.9-rc1..origin/dev: 349 PRs and 2 direct commits, none missing.

Checklist

• My code adheres to this project's style guidelines
• I have performed a self-review of my own code
• I have made pertinent documentation changes
• My changes do not introduce new warnings