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

instructions/dev/doc-pull-through.md

@@ -34,7 +34,7 @@ touched; a row that does not apply needs no action.
    | Touched surface | Document(s) that make a claim about it |
    |---|---|
    | A `wikitool` command's behaviour, flags, or interface | Its `cli_contract.CommandRecord` (name, synopsis, properties, exit status, retry policy - `tools/chemenu/cli_contract.py`), then `wikitool docs contract --apply` to regenerate its copy in [tools/CONTRACT.md](../../tools/CONTRACT.md) and `wikitool docs reference --apply` for the human reference under `docs/reference/` (a new group in `cli_contract.GROUPS` first needs its page there, with a title, a one-sentence head and the marker pair) |
-   | A stage's authoring rules (`raw/`, `kb/`, `types/`, `reports/`, `work/`, `tools/`, `instructions/`) | The touched `<stage>/CONTRACT.md` |
+   | A stage's authoring rules (`raw/`, `kb/`, `types/`, `reports/`, `work/`, `sites/`, `tools/`, `instructions/`) | The touched `<stage>/CONTRACT.md` |
    | A rule, gate, or invariant `AGENTS.md` itself states | The relevant `AGENTS.md` section (Invariants, Gates, File naming, Routing, ...) |
    | A workflow, stage, or command a human operates by hand | Whichever of `README.md`, `tools/README.md`, `INSTALL.md` or the pages under `docs/tutorials/`, `docs/how-to/` and `docs/reference/` names it - AGENTS.md § File naming says which document is for which reader. A new page goes into the area its kind of documentation belongs to; that area's `README.md` says which |
    | The reasoning behind a gate, boundary, or design decision | The `docs/explanation/` page that carries it, if one exists (AGENTS.md § File naming lists all seven reached from AGENTS.md itself, plus an eighth reached only from CLAUDE.md). **A decision with no page yet is the gap worth closing**: reasoning that lives only in a Gitea issue never ships - `dist export` carries `docs/explanation/` and no issue tracker, so a distributed instance gets the mechanism without the why |