sites: the instance writes its own site handlers as JSON files under sites/, the stack's learn.microsoft.com handlers become data files in the same format (#210); 10.0.0-beta.4

Files changed:
- .gitignore
- AGENTS.md
- CHANGES.md
- VERSION
- docs/explanation/architecture.md
- docs/how-to/README.md
- docs/how-to/write-a-site-handler.md
- docs/reference/commands/instance-health.md
- docs/reference/commands/raw-material-and-uploads.md
- docs/reference/configuration.md
- instructions/dev/doc-pull-through.md
- raw/CONTRACT.md
- sites/CONTRACT.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/commands/dist_cmd.py
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/git_publish.py
- tools/chemenu/commands/raw/fetch.py
- tools/chemenu/ownership.py
- tools/chemenu/sites/__init__.py
- tools/chemenu/sites/data.py
- tools/chemenu/sites/handlers/learn-microsoft-powershell-module.json
- tools/chemenu/sites/handlers/learn-microsoft.json
- tools/chemenu/sites/learn_microsoft.py
- tools/chemenu/sites/site.schema.json
- tools/chemenu/tests/test_dist_cmd.py
- tools/chemenu/tests/test_doctor.py
- tools/chemenu/tests/test_site_files.py
- tools/chemenu/toc.py

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

docs/reference/configuration.md

@@ -414,8 +414,9 @@ Size and quota are your deployment's decision, not defaults worth copying blindl
 derived text and prints hints about the page as `CHECK` lines; today there are two, both for
 `learn.microsoft.com`: `learn-microsoft` for every page of the host and
 `learn-microsoft-powershell-module` for a PowerShell module's overview page, which adds a hint
-naming the cmdlet pages it lists. Handlers are code in the stack - the instance does not write one.
-The `sites` section is what the instance decides about them, and it is optional: without it every
+naming the cmdlet pages it lists. Handlers are JSON files: the stack's, and the instance's own under `sites/`
+(see [How to write a site handler](../how-to/write-a-site-handler.md)).
+The `sites` section is what the instance decides about the handlers, and it is optional: without it every
 handler applies, in the locale `en-us`.
 
 - `disabled` switches handlers off by name. A page of that website is then handled as any other: