PR #2074 — Dispatch names a missing GOVERNS link before #1990 can block on it

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 completion oracle now reads the pull request the task actually named. The remaining velocity gap called out at the end of that work was the GOVERNS preflight: CLAUDE.md already describes a hard-fail (#1990) that dispatch does not enforce.

Strategic Shifts in This PR (if any)

No strategy change. #1990 stays the hard-fail. This PR only makes the gap visible, using option (a) from the 2026-10-06 velocity design, so in-flight epics are not blocked while that hard-fail is still unbuilt.

What This PR Shipped

• dispatch_agent() preflight checks whether --story, --issue, or --pr is resolvable. --issue still counts when it is auto-detected from #N in the task. --pr counts from an explicit number or from a pull request named in the task. An ad-hoc story-adhoc-* id created later does not count.
• When none of those is resolvable, preflight prints GOVERNS linkage missing — dispatch proceeding, but this will hard-fail once #1990 ships and writes the same line to sentinel.md as GOVERNS_LINKAGE_MISSING. The job still starts.
• A dispatch that already has a linked story keeps the previous path: no warning, and an explicit story with no goal still fail-closes (#2029).
• CLAUDE.md's #1990 notes (Hardened PR Review Policy and PR Review Discipline) now say this warning is live and distinct from the unbuilt hard-fail.
• Tests cover the warning plus a proceeding job, a linked story with no warning, and the unchanged unlinked-story hard-fail.

Plan: docs/superpowers/plans/2026-10-06-governs-velocity-unblock-plan.md §4. Design: docs/superpowers/specs/2026-10-06-governs-velocity-unblock-design.md §3.4.

Brainstorm Visuals Used

None. This follows the committed design and plan.

What This Achieved on the Path to Autonomy

An operator can see, in the dispatch log and in sentinel.md, that a job left without a GOVERNS link. The fleet can keep moving while #1990 is still open, instead of rediscovering the documentation gap by running a dispatch and watching nothing happen.

Strategic Note: The Goal at the End of This PR

#1990's hard-fail is the next enforcement step for this check. Until it ships, a missing --issue/--pr/--story warns and proceeds. Cross-harness review still closes #2073.