ci(desktop): a dispatched release waits on a first-parent commit

.github/workflows/desktop-release.yml

@@ -150,8 +150,10 @@ jobs:
             subject="${GITHUB_SHA}"
           else
             # A dispatch builds the tip; its checks are those of the newest
-            # commit that changed Desktop, whose tree the tip must equal.
-            subject="$(git log -1 --format=%H "${GITHUB_SHA}" -- .)"
+            # commit on main's own history (first parent) that changed
+            # Desktop, whose tree the tip must equal. A commit from inside a
+            # merged branch never had a Packages push run on main.
+            subject="$(git log -1 --first-parent --format=%H "${GITHUB_SHA}" -- .)"
           fi
           echo "Release checks follow ${subject}."
           echo "sha=${subject}" >> "${GITHUB_OUTPUT}"

tests/test_desktop_release_subject.py

@@ -0,0 +1,23 @@
+"""A dispatched Desktop release waits on a commit that has its own checks.
+
+Only commits on main's first-parent history get a Packages push run. A commit
+from inside a merged branch never does, so choosing it made the release gate
+wait 60 minutes for a run that cannot exist, then refuse (2026-10-20, 0.21.1).
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+WORKFLOW = Path(__file__).resolve().parents[1] / ".github/workflows/desktop-release.yml"
+
+
+def test_dispatch_subject_follows_first_parent_history() -> None:
+    lines = [
+        line.strip()
+        for line in WORKFLOW.read_text(encoding="utf-8").splitlines()
+        if line.strip().startswith('subject="$(git log')
+    ]
+    assert lines, "the release gate no longer chooses a subject commit with git log"
+    for line in lines:
+        assert "--first-parent" in line, line