Ad hoc: make the ladder executable, and make the collision class loud

record_check.py moves a finding along the cadence ladder and writes the
dated line into the finding at the same time — a check that is not
written down did not happen, which is the rule the register applies to
everyone else. make checked ARGS="RISK-F-0002 clean".

make check now also reports duplicate finding ids. The RISK-F-0004
collision was resolved by hand yesterday; the next one gets caught by the
tooling instead of by someone noticing a file listed twice.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/register_check.py

@@ -26,6 +26,16 @@ def main() -> int:
             lines.append(f"  {quiet}")
         lines.append("")
 
+    seen: dict[str, str] = {}
+    dupes = []
+    for f in lib.findings():
+        prior = seen.get(f["id"])
+        if prior:
+            dupes.append(f"{f['id']} — filed twice: {prior} and {f['_path'].name}; renumber the later commit")
+        seen[f["id"]] = f["_path"].name
+    if dupes:
+        section("Duplicate ids", dupes, "none")
+
     unknown = [
         f"{f['id']} — status '{f.get('status')}' is not one of {', '.join(lib.KNOWN_STATUSES)}; watched anyway"
         for f in fs