feat(pruefungen): acknowledge known findings so red means something again (#0104)

All three scheduled checks were permanently red, which is how a nine-day outage of
the canonize job went unnoticed: one more red cross among red crosses is invisible.
A check that can only ever be red cannot report anything.

An acknowledgement takes a known finding out of the red verdict without hiding it -
it still prints, with its reason and its deadline. Red is reserved for what is not
acknowledged, which is to say: for the new.

Three rules keep the list from becoming the next blind spot, which is the obvious
objection to this whole idea:

- Every entry needs a deadline. Once it passes, the entry stops acknowledging and
  says so, so the finding counts again.
- "Permanent" is only expressible as an ADR reference. A permanent exception
  without a decision record is already an error per AGENTS.md; here it cannot even
  be written down.
- An entry that matches nothing reports itself, so the file cannot quietly
  accumulate lines for problems that no longer exist.

Four entries to start: notfallhandbuch (ADR-0016, deliberately unmirrored),
threadnet-wiki (ADR-0015, the wiki mirrors the other way round), gameserver (sorb:
not part of ThreadNet - dated, so the ADR-or-move decision does not drift), and the
zero-job pipeline artifact.

Verified rather than argued, including the counter-proofs #0104 asks for: today
four are acknowledged and one real finding stays red; adding a fresh finding still
turns it red; and with the clock moved past the deadlines the dated entries stop
acknowledging and report themselves. The scope column was added after the first run
showed each check reporting the other's entries as ineffective.

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

scripts/stillstandspruefung.py

@@ -26,6 +26,12 @@ import subprocess
 import sys
 import urllib.parse
 from datetime import datetime, timedelta, timezone
+from pathlib import Path
+
+import quittungen
+
+# Repo-Wurzel: das Skript liegt in scripts/, die Quittungsliste daneben.
+ROOT = Path(__file__).resolve().parent.parent
 
 GITLAB = "https://git.lab/api/v4"
 GITEA = "https://rohana.axion1337.de/api/v1"
@@ -235,13 +241,20 @@ def main():
         for u in uebersprungen:
             print(f"  - {u}")
         print()
-    if befunde:
-        print(f"BEFUNDE ({len(befunde)}):")
-        for b in befunde:
+
+    # Bekanntes quittieren (#0104): Rot bleibt dem Neuen vorbehalten, sonst
+    # verliert die Alarmanlage ihre Aussage. Quittiertes verschwindet nicht,
+    # es zaehlt nur nicht mehr gegen die Pipeline.
+    offen, quittiert, meldungen = quittungen.anwenden(befunde, ROOT, "stillstand")
+    quittungen.ausgeben(quittiert, meldungen)
+
+    if offen:
+        print(f"BEFUNDE ({len(offen)}):")
+        for b in offen:
             print(f"  ! {b}")
         print("\nJeder Befund gehoert als Issue erfasst, nicht weggeklickt.")
         return 1
-    print("Keine Befunde.")
+    print("Keine offenen Befunde.")
     return 0