R-426: decoys for the release-complete gate

COVERS "release-complete": the working-tree gate runs in a scratch clone
whose origin is a scratch bare repo, against the fake Gitea. Convicted:
the newest `## vX.Y.Z` with no tag anywhere, a tag parked on an unrelated
commit, a tag with no package, and no-tag wins over a registry 500.
Inconclusive: a registry 500. Passed: the genuine release, an
`## Unreleased` heading above it, a newer version named only in prose or
under `###` (the withdrawn sweep decoy, now asserted the right way round),
a tag only origin has (the shallow-CI shape), and a LOCAL-only tag BY
DESIGN (CI's fresh clone and the published gate's converse probe see it).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

scripts/test_gate_decoys.py

@@ -52,6 +52,11 @@ COVERS = {
                  "lexical sorting would drop out of the retention window (0.9.x vs 0.10.x); a tags api answering 500 "
                  "or a non-JSON 200 is INCONCLUSIVE, never a pass - vs a clean registry, a non-semver tag and a version "
                  "older than the retention window (not asserted, BY DESIGN) (R-426)",
+    "release-complete": "the newest `## vX.Y.Z` with no tag anywhere, a tag parked on an unrelated commit, a tag "
+                        "with no package; a registry 500 is INCONCLUSIVE - vs the genuine release, an `## Unreleased` "
+                        "heading above it, a newer version named only in prose or under `###`, a tag that only "
+                        "origin has (the shallow-CI shape); a LOCAL-only tag passes BY DESIGN (CI's fresh clone "
+                        "and the published gate's converse probe are what see it) (R-426)",
 }
 
 fails = []
@@ -211,6 +216,68 @@ def published_cases(base):
     report("published: INCONCLUSIVE: Gitea unreachable", rc, out, 2, ("INCONCLUSIVE", "URLs tried"))
 
 
+# ── release-complete ─────────────────────────────────────────────────────────────────────────────
+def release_cases(base, ws):
+    bare = os.path.join(ws, "origin.git")
+    work = os.path.join(ws, "rc-work")
+    sh(["git", "clone", "-q", "--bare", "--no-tags", "file://" + ROOT, bare], ws)
+    sh(["git", "clone", "-q", "--no-tags", "file://" + bare, work], ws)
+    sh(["git", "config", "user.email", "decoy@gate.invalid"], work)
+    sh(["git", "config", "user.name", "decoy"], work)
+    # the WORKING-TREE gate, so the file under test is the one being edited, not HEAD's
+    shutil.copy(os.path.join(ROOT, "scripts", "check-release-complete.py"),
+                os.path.join(work, "scripts", "check-release-complete.py"))
+    sh(["git", "add", "scripts/check-release-complete.py"], work)
+    sh(["git", "commit", "-q", "--allow-empty", "-m", "the gate under test"], work)
+    base_sha = sh(["git", "rev-parse", "HEAD"], work)
+    ch = os.path.join(work, "CHANGELOG.md")
+    original = io.open(ch, encoding="utf-8").read()
+    V = "9.9.9"
+
+    def case(name, top, expect_rc, must=(), tag=None, origin_tag=False, packaged=True, pkg_status=None):
+        FAKE.reset()
+        if packaged:
+            FAKE.packages = {V}
+        FAKE.pkg_status = pkg_status
+        try:
+            io.open(ch, "w", encoding="utf-8").write(top + original)
+            sh(["git", "commit", "-q", "-am", name], work)
+            if tag == "head":
+                sh(["git", "tag", "-a", "v" + V, "-m", "decoy", "HEAD"], work)
+            elif tag == "unrelated":
+                empty = sh(["git", "mktree"], work)   # stdin is "" — the empty tree, written to this repo
+                orphan = sh(["git", "commit-tree", "-m", "unrelated", empty], work)
+                sh(["git", "tag", "-a", "v" + V, "-m", "decoy", orphan], work)
+            if origin_tag:
+                sh(["git", "push", "-q", "origin", "HEAD:refs/tags/v" + V], work)
+            rc, out = run([sys.executable, os.path.join(work, "scripts", "check-release-complete.py")],
+                          work, child_env(base))
+            report("release-complete: " + name, rc, out, expect_rc, must)
+        finally:
+            run(["git", "tag", "-d", "v" + V], work)
+            run(["git", "push", "-q", "origin", ":refs/tags/v" + V], work)
+            sh(["git", "reset", "-q", "--hard", base_sha], work)
+
+    HEAD = "## v%s — 2026-10-06\n\n- decoy release\n\n" % V
+    case("GENUINE: tagged at HEAD and published", HEAD, 0,
+         ("newest CHANGELOG version: v9.9.9", "is tagged, placed and published"), tag="head")
+    case("GENUINE: an `## Unreleased` heading above the release", "## Unreleased\n\n- wip\n\n" + HEAD, 0,
+         ("newest CHANGELOG version: v9.9.9",), tag="head")
+    case("GENUINE: a newer version named only in prose and under ###",
+         "The `## v10.0.0` heading is not written yet.\n### v10.0.0 notes\n\n" + HEAD, 0,
+         ("newest CHANGELOG version: v9.9.9",), tag="head")
+    case("GENUINE: the tag only on origin (the shallow-CI shape)", HEAD, 0,
+         ("exists on origin",), origin_tag=True)
+    case("BY DESIGN: a LOCAL-only tag passes (CI's fresh clone sees only origin)", HEAD, 0,
+         ("an ancestor of HEAD",), tag="head")
+    case("FACT: the newest heading has no tag anywhere", HEAD, 1, ("DOES NOT EXIST",))
+    case("FACT: a tag parked on an unrelated commit", HEAD, 1, ("NOT an ancestor",), tag="unrelated")
+    case("FACT: tagged, never published", HEAD, 1, ("IS NOT PUBLISHED",), tag="head", packaged=False)
+    case("INCONCLUSIVE: the registry answers 500", HEAD, 2, ("INCONCLUSIVE",), tag="head", pkg_status=500)
+    case("FACT beats INCONCLUSIVE: no tag AND the registry answers 500", HEAD, 1, ("DOES NOT EXIST",),
+         pkg_status=500)
+
+
 def main():
     srv = Server(("127.0.0.1", 0), Handler)
     threading.Thread(target=srv.serve_forever, daemon=True).start()
@@ -219,6 +286,7 @@ def main():
     print("agent gate decoys — fake Gitea at %s, scratch %s" % (base, ws))
     try:
         published_cases(base)
+        release_cases(base, ws)
     finally:
         srv.shutdown()
         srv.server_close()