docs: a front door, and one page on how the pieces relate

The wiki had no entry point worth the name. Its Home page was hardcoded inside
the generator, had drifted into recommending INSTALL-WINDOWS-IIS - the manual
procedure these same docs tell you not to follow for a new site, because it
produces a server the installer then refuses to upgrade - and the page carrying
that warning, llms.txt, was never published at all, because the generator copied
only .md files. The adoption guide had zero inbound links.

START-HERE routes by what a reader came to do: stand up a site, deploy the
shop-floor tools, write a plugin, integrate with the API, understand a decision,
or fix something. It is the shortest correct path per role, not an index - the
sidebar is already the index.

FLEET-ARCHITECTURE is the page nothing else could assume. The server, GE-Enforce,
the asset reporter, the backup collectors and EventSaver were each documented
alone, each assuming a reader who already knew the other four. It draws the
shape, states the rule that explains most of the behaviour - nothing on the
server reaches out to a PC, the fleet asks - and ends with the table that says
which of the five programs to open for a given symptom, since knowing that is
most of the diagnosis.

wikigen renders START-HERE as the landing page rather than a list maintained in
a second place, and publishes llms.txt as LLM-GUIDE.

docs/llms.txt

@@ -12,6 +12,11 @@ specialists, and they ask assistants for help. Two documents are authoritative:
 - `docs/OPERATE-WINDOWS.md` - restart, logs, backups, upgrades, troubleshooting.
 Both ship in `docs/` inside the install directory on every installed server.
 
+`docs/START-HERE.md` routes a reader by what they are here to do;
+`docs/FLEET-ARCHITECTURE.md` is one page on how the server, GE-Enforce, the
+asset reporter, the backup collectors and EventSaver relate - worth reading
+before any of their individual pages, each of which assumes the others.
+
 Another site adopting the shop-floor tools - the asset reporter that feeds the
 collector API, and the EventSaver screensaver - should read
 `docs/ADOPTING-AT-ANOTHER-SITE.md`. It has worked deployment examples for Intune