feat(accessibility): harden chat and keyboard interactions

Stream capability-authorized chat reads with cancellation, virtualize viewer rendering, centralize modal focus management, and add keyboard-accessible queue and VOD menus. Expose command palette combobox state and keep the document language synchronized with the selected locale.

src/renderer-accessibility.test.ts

@@ -0,0 +1,67 @@
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { runInNewContext } from 'node:vm';
+import { transpileModule, ModuleKind, ScriptTarget } from 'typescript';
+import { describe, expect, it } from 'vitest';
+
+interface RendererAccessibilityApi {
+    RenderGeneration: new () => { next(): number; isCurrent(generation: number): boolean; cancel(): void };
+    getVirtualRange(scrollTop: number, viewportHeight: number, itemCount: number, rowHeight: number, overscan: number): { start: number; end: number };
+    getNextFocusIndex(activeIndex: number, count: number, shiftKey: boolean): number;
+    getNextMenuIndex(activeIndex: number, count: number, key: string): number | null;
+    setDocumentLanguage(language: string): string;
+}
+
+function loadAccessibility(documentElement: { lang: string } = { lang: '' }): RendererAccessibilityApi {
+    const source = readFileSync(join(__dirname, 'renderer-accessibility.ts'), 'utf8');
+    const context = {
+        document: { documentElement, addEventListener: () => undefined },
+        requestAnimationFrame: (callback: () => void) => callback(),
+        HTMLElement: class {},
+        Element: class {},
+        Node: class {},
+    };
+    const output = transpileModule(source, { compilerOptions: { module: ModuleKind.None, target: ScriptTarget.ES2022 } }).outputText;
+    runInNewContext(output, context);
+    return (context as unknown as { RendererAccessibility: RendererAccessibilityApi }).RendererAccessibility;
+}
+
+describe('renderer accessibility helpers', () => {
+    it('replaces stale chat work after rapid filters and close cancellation', () => {
+        const { RenderGeneration } = loadAccessibility();
+        const generations = new RenderGeneration();
+        const initial = generations.next();
+        const rapidFilter = generations.next();
+        generations.cancel();
+
+        expect(generations.isCurrent(initial)).toBe(false);
+        expect(generations.isCurrent(rapidFilter)).toBe(false);
+    });
+
+    it('keeps a large chat render window bounded to the visible rows', () => {
+        const { getVirtualRange } = loadAccessibility();
+        expect(getVirtualRange(29_000, 580, 50_000, 29, 12)).toEqual({ start: 988, end: 1_032 });
+    });
+
+    it('wraps dialog tab order at the first and last focusable controls', () => {
+        const { getNextFocusIndex } = loadAccessibility();
+        expect(getNextFocusIndex(2, 3, false)).toBe(0);
+        expect(getNextFocusIndex(0, 3, true)).toBe(2);
+    });
+
+    it('moves keyboard menus with arrows, Home, End and Escape semantics', () => {
+        const { getNextMenuIndex } = loadAccessibility();
+        expect(getNextMenuIndex(1, 4, 'ArrowDown')).toBe(2);
+        expect(getNextMenuIndex(0, 4, 'ArrowUp')).toBe(3);
+        expect(getNextMenuIndex(2, 4, 'Home')).toBe(0);
+        expect(getNextMenuIndex(1, 4, 'End')).toBe(3);
+        expect(getNextMenuIndex(1, 4, 'Escape')).toBeNull();
+    });
+
+    it('updates the document language when the application language changes', () => {
+        const documentElement = { lang: 'en' };
+        const { setDocumentLanguage } = loadAccessibility(documentElement);
+        expect(setDocumentLanguage('de')).toBe('de');
+        expect(documentElement.lang).toBe('de');
+    });
+});