backup: an instance backs up into a synced folder - backup init makes a bare repository under <target>/git its origin, backup run and publish mirror the machine data into <target>/<machine>/, doctor warns about .git in a synced folder (#186); 10.0.0-beta.10

Files changed:
- CHANGES.md
- INSTALL.md
- VERSION
- docs/explanation/configuration-tiers.md
- docs/how-to/README.md
- docs/how-to/back-up-to-a-synced-folder.md
- docs/reference/commands/README.md
- docs/reference/commands/git.md
- docs/reference/commands/instance-health.md
- docs/reference/configuration.md
- instructions/publish-cycle.md
- instructions/setup-instance.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/backup.py
- tools/chemenu/cli.py
- tools/chemenu/cli_contract.py
- tools/chemenu/commands/backup_cmd.py
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/git_publish.py
- tools/chemenu/config_shapes.py
- tools/chemenu/reference_doc.py
- tools/chemenu/tests/conftest.py
- tools/chemenu/tests/test_backup.py
- tools/chemenu/tests/test_config_shapes.py

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

INSTALL.md

@@ -100,7 +100,9 @@ repository:
   needed).
 - <!-- setup-question: remote --> **Remote** - for an empty clone, only the confirmation that
   `origin` is right; otherwise a URL, if you want to push to a server. Without a remote the
-  instance stays local, and every `publish` runs with `--no-push`.
+  instance stays local, and every `publish` runs with `--no-push`. Without a git server but with a
+  synced folder (OneDrive and the like), the agent offers a backup into that folder instead:
+  [docs/how-to/back-up-to-a-synced-folder.md](docs/how-to/back-up-to-a-synced-folder.md).
 - <!-- setup-question: kb-language --> **Language and tone of the pages** - they go into
   `kb/CONVENTIONS.md`, plus `kb/<name>/COLLECTION.md` per collection. Ready-made profiles,
   including a complete German one, are in `instructions/kb-profiles.md`. Decide this **before the