Astra round 5 brief: instance key provision, rev 4

Review: docs/superpowers/plans/2026-10-10-instance-key-provision.md, rev 4 (3e42e8e7). It answers your round 4 (CODEX-PLAN-INSTANCE-KEY-R4.md). Ruling 26 is Paul's decision: a replica gets its home's key. It replaces rulings 17 and 25. The rev 3.1 strip is reverted.

Mechanism. Before any replica process starts, the agent allows it to run in only two cases:

• with exactly its home's key, verified against the home key's digest;
• with no key but with a control socket, so that the helper refuses instead of minting.

With no key and no socket (seeds, claim launches before O6, a failed socket bind), the agent refuses the launch itself.

A pre-roll check records verified home keys in CARLOS_REPLICA_HOME_KEYS before any box is upgraded. Replicas that already share their home's configured key therefore keep working.

New obligation O8 (replica placements, #162). The replica record names its home. The replica reads the home's published <host>.env item, verifies it by digest, and writes it create-only. Until O8 lands, a keyless replica refuses to start.

Judge:

1. Are both round 4 findings closed?
2. Is the replica refusal reliable on every launch path (seed, spawn, nested, claim, socket-bind failure)?
3. Can a replica ever run with a key other than its home's?
4. Is the pre-roll check sound? Is CARLOS_REPLICA_HOME_KEYS safe: is it exposed to the tenant, is it in logs?
5. Is O8 well-defined, and is its fallback safe?
6. Anything new?

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