feat: add consented Relay review handoff

[quinn-code-agent]

Summary

• add one clear-consent, fail-closed Relay sharing operation that returns only a validated Room URL and authoritative expiry
• add a Room-scoped background feedback watcher with persistent dedupe, exact Result verification, immutable Slack origin binding, readiness/reuse, and verified shutdown
• harden private owner/watch state, expiry, redirect, Result identity, and process identity boundaries
• remove the duplicated Hermes Web viewer; hosted browser review remains owned by subspace-relay

User interaction

1. Hermes recognizes an explicit request to review one finished artifact.
2. It performs local/capability preflight and discloses bearer-link, format/size, expiry, and retention limits.
3. Only a clear Yes starts immutable create → verify → package → publish → Room.
4. Slack receives only the safe Room URL plus actual expiresAt.
5. A detached Room watcher owner-pulls and verifies feedback, deduplicates Result IDs, and emits a safe advisory event to the dispatch-bound origin thread without advancing workflow state.

Verification

• python3 -m unittest tests.test_relay_consent -v — 12/12 passed
• python3 -m unittest tests.test_relay -v — 14/14 passed
• python3 -m unittest discover -s tests -v — 57/57 passed
• python3 -m py_compile __init__.py bin/subspace-review-gate bin/subspace-review-relay bin/subspace-review-runtime tests/test_relay.py tests/test_relay_consent.py — passed
• git diff --check origin/main..HEAD — passed
• fresh cycle-3 adversarial validation passed forged argv/PID reuse no-signal, readiness/reuse/verified stop, expiry/private-state/redirect/Result/origin/dedupe boundaries

Safety and delivery state

• Draft only
• no real Relay publication from the implementation tests
• no live Hermes runtime apply
• no merge, release, or deploy authorization
• exact-final-SHA independent review is still required before merge