fix: pre-landing review fixes (dispatch-ci skips a workflow the branch predates; harness decision; changelog fragment)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

lib/ship-queue-dispatch-ci.ts

@@ -9,7 +9,10 @@
  * run at this head already concluded), a wait for each run, and one
  * `PREGATE_CLEARED:` per requires-remote lane whose workflow is one of them
  * and whose run concluded success. A red run clears no lane and refuses. A
- * fork head is never dispatched here (QUEUE_TRAIN_UNTRUSTED).
+ * fork head is never dispatched here (QUEUE_TRAIN_UNTRUSTED). A workflow the
+ * base has but the head predates (windows-smoke.yml on a branch cut before it
+ * landed) is skipped with a note: GitHub reads the workflow file from the
+ * branch, so the dispatch could only fail.
  */
 import * as fs from 'node:fs';
 import * as path from 'node:path';
@@ -17,6 +20,7 @@ import type { PregateFile } from './headless-artifacts';
 import { PREGATE_OUT_REL, clearObligation, readPregateFile, writePregateFile } from './pregate/index';
 import type { QueueContext } from './ship-queue';
 import type { QueueFailure } from './ship-queue-gate';
+import { git } from './ship-queue-gate';
 import { prInfo, repoSlug, runView } from './ship-queue-train-github';
 
 const sleep = (ms: number) => new Promise(resolve => setTimeout(resolve, ms));
@@ -47,6 +51,11 @@ export async function dispatchCi(ctx: QueueContext, o: DispatchCiOptions): Promi
     const prior = atHead.find(r => r.status === 'completed');
     if (prior) { lines.push(`CI_DISPATCH: ${wf} not dispatched (run ${prior.databaseId} already concluded ${prior.conclusion ?? 'unknown'} at this head)`); concluded.set(wf, prior); continue; }
     const live = atHead[0];
+    const wfPath = `.github/workflows/${wf}`;
+    if (!live && git(ctx.repoRoot, ['cat-file', '-e', `${head}^{commit}`]).ok && git(ctx.repoRoot, ['cat-file', '-e', `${ctx.remote ?? 'origin'}/${ctx.base}:${wfPath}`]).ok && !git(ctx.repoRoot, ['cat-file', '-e', `${head}:${wfPath}`]).ok) {
+      lines.push(`CI_DISPATCH: ${wf} not dispatched (${wfPath} is on ${ctx.base} but not in ${head.slice(0, 12)}; the branch predates it, so its pull_request run comes with the stamp commit)`);
+      continue;
+    }
     if (!live) {
       const d = ctx.gh(['workflow', 'run', wf, '--ref', branch]);
       if (!d.ok) return { lines, failure: { code: 'QUEUE_NOT_READY', message: `gh workflow run ${wf} --ref ${branch} failed (${(d.err ?? d.out).trim().replace(/\s+/g, ' ').slice(0, 120) || 'no output'})` } };