feat(fp): WP-17 — app-level a11y: route focus, template lint, WCAG checklist

Adds route-change focus management (new page's h1, afterNextRender) plus
scroll-position restoration wired once in app.config.ts; angular-eslint's
templateAccessibility bundle linting every inline template via
processInlineTemplates (verified firing with a planted violation, one real
hit fixed in rich-text-editor); docs/wcag-checklist.md and Foundations/
Accessibility MDX tying the four a11y layers (axe, lint, play tests,
manual checklist) together. The checklist pass already earned its keep —
it found a real 320px overflow in aanvraag-block's warning alert.

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

src/app/shared/layout/route-focus.ts

@@ -0,0 +1,45 @@
+import {
+  DOCUMENT,
+  ENVIRONMENT_INITIALIZER,
+  EnvironmentInjector,
+  afterNextRender,
+  inject,
+} from '@angular/core';
+import { NavigationEnd, Router } from '@angular/router';
+
+/** Template-layer wiring (not a component): on every route change after the
+    initial load, moves focus to the new page's `<h1>` (page-shell always
+    renders one) so screen-reader/keyboard users land on the new content
+    instead of wherever focus happened to be. Falls back to `#main` (the
+    shell's landmark) if a page has no heading. Deferred via `afterNextRender`
+    so it doesn't race Angular's view-transition DOM swap. */
+export function provideRouteFocus() {
+  return {
+    provide: ENVIRONMENT_INITIALIZER,
+    multi: true,
+    useValue: () => {
+      const router = inject(Router);
+      const document = inject(DOCUMENT);
+      const injector = inject(EnvironmentInjector);
+      let isInitialLoad = true;
+
+      router.events.subscribe((event) => {
+        if (!(event instanceof NavigationEnd)) return;
+        if (isInitialLoad) {
+          isInitialLoad = false;
+          return;
+        }
+        afterNextRender(
+          () => {
+            const target =
+              document.querySelector<HTMLElement>('#main h1') ?? document.getElementById('main');
+            if (!target) return;
+            target.setAttribute('tabindex', '-1');
+            target.focus({ preventScroll: true });
+          },
+          { injector },
+        );
+      });
+    },
+  };
+}

src/app/shared/ui/rich-text-editor/rich-text-editor.component.ts

@@ -161,6 +161,7 @@ export interface PlaceholderOption {
       #editor
       class="rte-editable"
       [attr.contenteditable]="editable()"
+      [attr.tabindex]="editable() ? '0' : null"
       (input)="emit()"
       (keydown)="onKeydown($event)"
       role="textbox"