Changelog catchup: PRs since v0.8.0

[phinze]

Mid-cycle changelog update. Catches the Unreleased section up to date with PRs that merged since v0.8.0:

• doctor: add QUIC reachability check for the API port #819 — doctor QUIC check
• validate: allow tls.additional_names / tls.additional_ips in behind-proxy-http #820 — tls.additional_names / additional_ips accepted in behind-proxy-http
• MIR-1159: keep ephemeral pools at 1 sandbox and fix lease URL races #821 — ephemeral pool scaling + activator lease URL races
• Fix send-on-closed-channel panic in deploy explain mode #822 — deploy explain-mode panic + stuck 30m server lock
• Improve admin CLI per-method parameter help UX (MIR-746) #823 — admin CLI per-method help UX
• Restart miren.service after register instead of warning #824 — server register restarts the systemd unit instead of warning

CI hygiene PRs excluded: #818 (pin GHA SHAs) and #826 (docker release artifact race) — neither has user-visible behavior change.

#817 (GitHub auth + auth provider add reshape) was already landed in the Unreleased section.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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• docs/docs/changelog.md

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📝 Walkthrough

Walkthrough

This PR updates the Unreleased section of the changelog with new entries documenting recent improvements and bug fixes. The improvements cover QUIC reachability probing in miren doctor server, automatic systemd unit restarts in miren server register, and enhanced help output in miren admin. Bug fix entries document resolutions for deploy lock timeout issues, ephemeral preview deploy scaling problems, and TLS certificate SAN validation in proxy HTTP mode.

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_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Actionable comments posted: 0

[maryelizbeth]

LGTM