ci: add release docs workflow

[zbeyens]

Summary

• Add generated /docs/releases feed backed by Version Packages PR data, including the v49+ backfill and release sidebar move.
• Update release automation to sync release docs, preserve package tags for compare links, and generate validated repo-level release notes.
• Sync the related agent/browser tooling, release plans, and solution docs captured during the workflow work.

Verification

• pnpm check
• $codex-review clean after fixes
• Browser verified /docs/releases and old migration redirects

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Latest commit: 25eea55

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[chatgpt-codex-connector]

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