test(language-server): add end-to-end verification for HTML editing support

Adds a scratch page (kept intentionally, per controller ruling on Task 8)
and one end-to-end test that drives the real language server over LSP
stdio against that page's real text, verifying completion (with the
seo-block negative case tested via a simulated '<' keystroke and
mutation-verified against html-regions.ts), hover, folding ranges,
linked editing, and wrn/tagComplete all work together on realistic
content.

Regenerates routes.gen.ts and wrnexus.generated.d.ts for the new page's
route, required by check:generated-types.

Two checks from the original brief (auto-close-tag insertion and Emmet
Tab-expansion) require a live VS Code Extension Development Host and
are documented as outstanding manual verification in
.superpowers/sdd/2026-08-18-wrn-html-editing/task-8-report.md.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

examples/basic-app/app/routes.gen.ts

@@ -9,6 +9,7 @@ export interface Routes {
   "/client-only": Record<string, never>;
   "/dashboard": Record<string, never>;
   "/hello": Record<string, never>;
+  "/html-editing-check": Record<string, never>;
   "/island-demo": Record<string, never>;
   "/language-tools": Record<string, never>;
   "/layout": Record<string, never>;
@@ -32,6 +33,7 @@ export interface RouteNames {
   "client.only": "/client-only";
   "dashboard": "/dashboard";
   "hello": "/hello";
+  "html.editing.check": "/html-editing-check";
   "island.demo": "/island-demo";
   "language.tools": "/language-tools";
   "layout": "/layout";
@@ -124,6 +126,7 @@ export function route<N extends RouteName>(
   "client.only": "/client-only",
   "dashboard": "/dashboard",
   "hello": "/hello",
+  "html.editing.check": "/html-editing-check",
   "island.demo": "/island-demo",
   "language.tools": "/language-tools",
   "layout": "/layout",