ADR 0169 → 0170: the firewall seat's record renumbered after a collision on main; its built note; cycle.py refuses two records sharing a number

Another session's 0169 landed first. The collision check from issue 155
covered issue folders only; it covers decision records now, and would have
refused this.

00-META/checks/cycle.py

@@ -131,6 +131,22 @@ def main():
         else:
             seen[number] = name
 
+    # And decision records, which 155's fix left out: on 2026-10-02 two ADRs numbered 0169 landed
+    # on main from two sessions within the hour, and every check passed.
+    seen_records = {}
+    for path in sorted(glob.glob(os.path.join(ROOT, "02-DECISIONS", "[0-9]*.md"))):
+        name = os.path.basename(path)
+        number = name.split("-", 1)[0]
+        if not number.isdigit():
+            continue
+        if number in seen_records:
+            bad(os.path.join("02-DECISIONS", name),
+                "is numbered %s, and so is %s -- a record's number is how it is cited. Take the next "
+                "free number across main AND every open pull request; the branch that lands last "
+                "renumbers" % (number, seen_records[number]))
+        else:
+            seen_records[number] = name
+
     for path in sorted(glob.glob(os.path.join(ROOT, "04-ISSUES", "*", "00-report.md"))):
         front = frontmatter(path)
         if front is None: