The manual as a site: a landing page, the chapters, and a page per module

index.sz is a landing page pointing to the manual, now manual.sz, and to
modules/, where each library module has a page made by @generate-docs from
the docs it was compiled with. The chapters gain appendices, and part III
links each module to its page. glasnost's page cache is ignored.

🤖 Generated with [ECA](https://eca.dev) (anthropic/claude-opus-5-5)

Co-Authored-By: eca-agent <git@eca.dev>

modules/index.sz

@@ -0,0 +1,6 @@
+(meta (title "Modules")
+      (sort title))
+
+The reference for each library module. Every page is made from the
+documentation the module was compiled with, so it says what the installed
+module does.