ARC-Client release pipeline -- tracker for #38 + #39 auto-update rollout

[ComfyChloe]

Tracking issue for the two-phase auto-update rollout.

Relationship

• Phase A (infrastructure): Auto-update Phase A: CI workflow + GitHub Releases manifest + verification gates #38
• Phase B (client runtime + UI + force-update gate): Auto-update Phase B: client runtime + UI + force-update gate #39 — currently blocked behind Phase A

Goal

One place to track the end-to-end release pipeline: signed builds produced by CI, a GitHub Releases manifest the client can query, and a runtime that verifies, applies, and (when required) forces updates.

Acceptance criteria

• Auto-update Phase A: CI workflow + GitHub Releases manifest + verification gates #38 merged: CI workflow builds + signs artifacts, publishes a Releases manifest with verification hashes
• Auto-update Phase B: client runtime + UI + force-update gate #39 unblocked and merged: runtime verifies the manifest, applies updates, enforces the force-update gate when configured
• A real release published through the pipeline and installed cleanly by an existing client
• Rollback/failure behavior documented (what the client does on a bad update)

This issue closes only when a real release has shipped through the full pipeline.