Complete landing workflow v1: merge-ready queue on the gunbc-served dashboard lane — only PRs at the operator decision boundary, typed blockers for everything else, evidence inspection, one admitted merge/enqueue action; thin actor projections, no Actor carrier

[gunbai-bot]

Worker attestation

• Title describes the change.
• PR body summarizes what and why.
• Focused tests are named below and pass.
• No GitHub issue is closed; this is dashboard work item node://adhoc-1b15279f-21c.
• Commits are this session’s implementation plus the session-dashboard WIP snapshots and merges of current main.
• No secrets, credentials, generated binaries, or large artifacts are staged.

Summary

Adds landing workflow v1 to the existing gunbc-served dashboard. The landing page projects the dashboard-owned merge_criteria summary into a merge-ready queue or exhaustive typed blocker rows, exposes review/check evidence, shows untracked GitHub PRs outside admission, and offers one server-re-admitted exact-head squash-merge action with a receipt. Actor information remains a thin projection over existing work-item/session/provider/branch facts; no Actor carrier is introduced.

The live seam is fail-closed: unavailable or malformed dashboard/GitHub observations refuse, malformed authority rows are validated before eligibility filtering, duplicate PR bindings refuse, summary ready/requirement divergence refuses, operator merge intent is server-issued, observe-only instances cannot actuate, and the POST re-observes admission before GitHub CLI enforces exact-head matching.

Test plan

• PASS: 15 focused claim_batch landing workflow witnesses, including ready-only queue, first-review blocker, stale-head approval exclusion, exhaustive blockers, divergence refusal, exact-head refusal, intent-token refusal, duplicate-binding refusal, malformed review evidence refusal, malformed pre-filter PR row refusal, and bounded dashboard transport.
• PASS: focused roadmap serve witnesses for POST-only merge binding and observe-only refusal before effects.
• PASS: corpus external-authority lens witnesses after canonical authority naming.
• PASS: cargo fmt --all --check and git diff --check.