website: fix nine review findings (generator coverage, loader facts, mode semantics)

Generator (all four structural gaps):
- harness service pages now render public properties/accessors, not just
  methods (ctx.codeRuntime.language/isolation were missing);
- the class page merges the same-named interface half, so ctx.root/baseUrl/
  events/logger/reflect/registry appear on Context (vendor root JSDoc gains
  prose alongside @experimental);
- Pick<…> heritage on a Context merge resolves to the picked class members,
  giving ctx.effect a documented signature on the Fiber page;
- {@link} tags normalize to code spans; merge sections get their own h2 so
  reflect members no longer nest under 'Static members'.

verify-website-yaml: reject the unloadable 'group:' pseudo-name (tree.import
only special-cases 'cordis:'; no builtin is registered here) and recurse into
@cordisjs/plugin-group nested entry lists instead.

Prose corrected against loader/cordis source: service.md isolation example
uses the real group plugin + group: true + the required isolate map;
config.md documents concurrent entry startup (Promise.all; order via inject)
and the real hmr defaults (root ['.'], base/ignored/debounce); events.md
fixes emit (synchronous, not parallel), bail (null/false also delegate), and
serial (stops at the first bail value).

vendor/cordis/src/context.ts

@@ -18,7 +18,7 @@ export interface Context {
   [symbols.isolate]: Dict<symbol>
   /** Intercept map: service name → config merged into that service's per-plugin config. */
   [symbols.intercept]: Dict
-  /** @experimental */
+  /** The root context of the application (every child context shares it). @experimental */
   root: this
   /** Base URL used to resolve relative plugin/module specifiers, if the runtime sets one. */
   baseUrl?: string