feat: bug-report collector tools/bugreport.py and instructions/bug-report.md (#157)

Files changed:
- .gitea/workflows/ci.yml
- CHANGES.md
- INSTALL.md
- VERSION
- instructions/bug-report.md
- instructions/gates.md
- instructions/setup-instance.md
- instructions/upgrade-instance.md
- reports/CONTRACT.md
- tools/README.md
- tools/bugreport.py
- tools/chemenu/tests/test_bugreport.py

instructions/setup-instance.md

@@ -305,6 +305,10 @@ and ready for its first ingest.
     afterwards are `wiki-ingest`, `wiki-query`, `wiki-manage`, `wiki-lint`, `wiki-status` and
     `gtd-weekly-review` available.
 
+**A step fails and the cause is not obvious?** Do not improvise around it (invariant 7). Offer the
+user a bug report - [bug-report.md](bug-report.md) - and run it only if they agree; the collector
+works even when `wikitool` does not start.
+
 ## Scope
 
 Applies only to an empty distribution produced by `dist export`. For an existing clone of this