Astra round 7 brief: instance key provision, rev 5.1 (confirming)

Review: docs/superpowers/plans/2026-10-10-instance-key-provision.md rev 5.1 (7a2e4696). It answers your round 6 (CODEX-PLAN-INSTANCE-KEY-R6.md).

Changes:

• Ruling 29. The replica gate takes the key's source from the same read that builds the launch environment, and never re-reads it. An interleaving test rewrites config between that read and the gate, and the gate refuses.
• Ruling 30. The digest list moves from the agent's env into /etc/carlos/replica-home-keys. Only the pre-roll check writes it, as a whole file renamed into place. The agent re-reads it on every replica launch and caches nothing. The procedure keeps replicas stopped and confirms the file no longer names them before the key changes.
• Task 1 is now built and reviewed (c568c13b..e8487c3a on this branch). The plan's Task 1 code was copied from the branch, including a canonical-bytes check in ParseAdoption. A mixed-version rollout note is added.

Judge:

1. Are both findings closed?
2. Is the per-launch file read safe? Consider a partial write, a missing file, permissions, and whether the tenant can see or write it.
3. Does Task 1's committed code match the plan, and does anything else in the plan rely on the looser parser?
4. Anything new?

Give findings P1/P2/P3 with file:line, then a verdict: ready to build, or not.