v0.15.11 — fix(task): the merge-gate could not tell a PR the task DELIVERED from a PR it REPORTS ON (DIVE-1965)

The gate treated every PR number in a close as a delivery claim, so a review/triage/audit close that merely CITED another task's PR was judged against it. Default is now CITED: delivery must come from delivery_ref, a Branch: line, a Delivered: line, or a shipping verb adjacent to the ref ('merged as PR #6', 'landed in #13'); negations rejected. A cited ref is not resolved, not refused, not stamped.

The asymmetry is deliberate and the cheap side is ANNOUNCED — the close warns which refs were set aside, names both escapes, and emits a task.merge-gate-reported-on audit row; citations are skipped BEFORE the 5-ref cap so they cannot crowd out the real delivery. Pinned invariant: a close naming its own merged+green delivery plus two cited OPEN PRs closes clean, unrefused AND unstamped.