instructions, docs, tools: Export - setup-instance und How-to nennen auch die ganze KB, page_export-Docstring nennt die Index-Dateien (#217 close); 10.1.0-beta.22

Files changed:
- CHANGES.md
- VERSION
- docs/how-to/export-to-a-synced-folder.md
- instructions/setup-instance.md
- tools/chemenu/page_export.py

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

tools/chemenu/page_export.py

@@ -13,7 +13,8 @@ properties that carry that, each with a test:
 - **Deterministic.** A file depends on its page, the selection it links into
   and the commit that last touched that page - no timestamp, no `HEAD` - so a
   run on an unchanged corpus writes nothing, not even a file's modification
-  time, and a commit to one page rewrites that page's file alone.
+  time, and a commit to one page rewrites that page's file alone - plus,
+  with `index: true`, the index files that list it (`chemenu.export_index`).
 - **Only its own files are touched.** What an earlier run wrote is recorded in
   a manifest in the target (`.wikitool-export.json`, with a digest per file).
   A run removes only manifest files that are no longer exported, leaves every