PR #2070 — Completion oracle reads the PR the task actually named

The Broader Goal at the End of the Previous PR

v0.24.0 still needs a dispatch to move from implementation to a trusted review verdict on GitHub state alone. The GOVERNS velocity plan's role check landed first. The completion oracle was the remaining reason a real review could look like insufficient_evidence.

Strategic Shifts in This PR (if any)

No strategy change. --issue stays the GOVERNS link. It is no longer allowed to stand in for a different pull request named in the task.

What This PR Shipped

• Dispatch stores gh_write_target as the PR named in the task when that number is not the --issue link, and records it on daemon_jobs.cross_branch_pr.
• The terminal check calls gh pr view <N> --json reviews,commits,headRefName and keeps events at or after the job's start time. A review-only job with an empty worktree completes from that review. A fix job that pushed onto another PR completes from a new commit on that PR.
• When the PR head is this job's own branch, or no cross-branch PR was recorded, completion still uses the local diff.
• Tests cover the #2056 mismatch (--issue 2051 vs PR #2054), a fresh commit on another PR, and the unchanged in-worktree path.

Plan: docs/superpowers/plans/2026-10-06-governs-velocity-unblock-plan.md §1. Design: docs/superpowers/specs/2026-10-06-governs-velocity-unblock-design.md §3.1.

Brainstorm Visuals Used

None. This follows the committed design and plan.

What This Achieved on the Path to Autonomy

A review dispatch can be trusted when the review lands on the PR the task named, without a manual gh pr view to overturn a false insufficient_evidence verdict.

Strategic Note: The Goal at the End of This PR

The next velocity items are reviewer-logged cost provenance and the GOVERNS preflight warning. This PR does not merge itself; cross-harness review still closes #2056.