chore: amend v1.0.0 release notes with Fast restart fix

[mrubens]

Amends the unshipped 1.0.0 changelog section on develop so the pending release candidate can be refreshed from the latest develop tip.

What changed

• Adds one patch bullet to the existing ## 1.0.0 section covering [Fix] Fast sessions get stuck when API restarts during retry recovery #1944 (Fast sessions stuck when the API restarts mid-conversation), generated via pnpm run version -- --amend.
• [Refactor] Remove obsolete Fast payload compatibility #1934 (internal refactor) and [Fix] Promotion PR metadata can reference a stale candidate #1951 (release-CI fix) ship without changelog bullets; no public docs updates are needed for any of the three post-cut commits.

Validation

• pnpm test:release-scripts — pass
• Diff is exactly one generated CHANGELOG.md line; root version stays 1.0.0, no pending changesets remain, no workspace package versions changed.

Follow-up

After this merges, the Release workflow will be dispatched with version=1.0.0 to fast-forward release/v1.0.0 (Promote PR #1950) from develop.

[roomote-community]

No code issues found. See task

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