CC-528: Accept generic Gate results for publish

[screenleon]

Summary

• define publication policy compatibility so a current generic Gate GO satisfies the publish baseline while maintainer remains preferred
• keep the explicit maintainer consumer strict and fail closed for unknown consumers
• let pmctl ship finish --gate-result reuse a current-tree initial Gate artifact without running a replacement Gate
• preserve targeted remediation boundaries: a targeted artifact alone cannot authorize publication
• document the policy coordinates and add CC-529 as a bounded observability follow-up

Why

generic and maintainer are consumer policies, not identities or permission levels. Both use the same tier, risk-signal, reviewer, and verification contracts. The previous publish verification treated maintainer as a hard minimum, so a valid current generic GO could not be reused even though it should satisfy the baseline publication requirement.

This change separates required policy from preferred policy: publish accepts generic as baseline and reports maintainer as preferred, while direct maintainer verification still requires a maintainer artifact.

User and developer impact

• everyday /pr-gate results can be reused for publication when they are valid, current, initial-pass artifacts
• maintainers still get stronger assurance when the artifact was produced under maintainer
• ship finish retains its clean-tree, HEAD-drift, full-suite, push, and PR guards
• malformed policy metadata and unknown policy consumers fail closed

Validation

• Claude Sonnet 5 PR Gate: GO under generic, full tier, parallel mode, all five reviewer dimensions (run before the docs-only CC-529 follow-up; the follow-up was explicitly accepted without re-gating)
• tests/bin/run-all-tests.sh: 97 passed, 0 failed, 0 skipped
• test-pr-gate: 211 passed
• test-pmctl-gate: 69 passed
• test-pmctl-ship: 79 passed
• ./cli/pmctl backlog lint
• git diff --check

Follow-up

CC-529 tracks surfacing embedded_policy, required/preferred policy, and policy_satisfaction consistently in ship stdout, PR bodies, and finish markers. It does not change the policy floor introduced here.