tools: Export - include "all" wählt die ganze KB, index: true schreibt index.md und INDEX.md in den Zielordner (#217); 10.1.0-beta.21

Files changed:
- CHANGES.md
- VERSION
- docs/how-to/export-to-a-synced-folder.md
- docs/reference/commands/exports.md
- docs/reference/configuration.md
- raw/CONTRACT.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/catalog.py
- tools/chemenu/commands/export_cmd.py
- tools/chemenu/commands/index_build.py
- tools/chemenu/config_shapes.py
- tools/chemenu/export_index.py
- tools/chemenu/guideline_export.py
- tools/chemenu/page_export.py
- tools/chemenu/tests/test_config_shapes.py
- tools/chemenu/tests/test_export_run.py
- tools/chemenu/tests/test_index_build.py

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

VERSION

@@ -1 +1 @@
-10.1.0-beta.20
+10.1.0-beta.21