refactor: move document transcription, annotation, viewer sub-packages

- transcription/: TranscriptionBlock, Column, EditView, PanelHeader, ReadView,
  Section + transcriptionMarkers, blockConflictMerge, saveBlockWithConflictRetry
  + useBlockAutoSave, useBlockDragDrop hooks
- annotation/: AnnotationLayer, AnnotationShape, AnnotationEditOverlay
- viewer/: PdfViewer, PdfControls + useFileLoader, usePdfRenderer hooks

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/document/annotation/AnnotationEditOverlay.svelte.test.ts

@@ -0,0 +1,71 @@
+import { describe, it, expect } from 'vitest';
+import { render } from 'vitest-browser-svelte';
+import AnnotationEditOverlay from './AnnotationEditOverlay.svelte';
+import type { Annotation } from '$lib/types';
+
+const annotation: Annotation = {
+	id: 'ann-1',
+	documentId: 'doc-1',
+	pageNumber: 1,
+	x: 0.1,
+	y: 0.2,
+	width: 0.3,
+	height: 0.4,
+	color: '#00c7b1',
+	createdAt: '2026-01-01T00:00:00Z'
+};
+
+describe('AnnotationEditOverlay', () => {
+	it('renders 8 handle elements', async () => {
+		render(AnnotationEditOverlay, { annotation });
+
+		const handles = document.querySelectorAll('[data-handle]');
+		expect(handles).toHaveLength(8);
+	});
+
+	it('renders handles for all four corners and four edge midpoints', async () => {
+		render(AnnotationEditOverlay, { annotation });
+
+		expect(document.querySelector('[data-handle="nw"]')).not.toBeNull();
+		expect(document.querySelector('[data-handle="ne"]')).not.toBeNull();
+		expect(document.querySelector('[data-handle="sw"]')).not.toBeNull();
+		expect(document.querySelector('[data-handle="se"]')).not.toBeNull();
+		expect(document.querySelector('[data-handle="n"]')).not.toBeNull();
+		expect(document.querySelector('[data-handle="s"]')).not.toBeNull();
+		expect(document.querySelector('[data-handle="e"]')).not.toBeNull();
+		expect(document.querySelector('[data-handle="w"]')).not.toBeNull();
+	});
+
+	it('each handle has a 44x44 hit area', async () => {
+		render(AnnotationEditOverlay, { annotation });
+
+		const hitAreas = document.querySelectorAll('[data-handle-hit]');
+		expect(hitAreas).toHaveLength(8);
+		hitAreas.forEach((el) => {
+			expect(el.getAttribute('width')).toBe('44');
+			expect(el.getAttribute('height')).toBe('44');
+		});
+	});
+
+	it('renders a move area covering the full box', async () => {
+		render(AnnotationEditOverlay, { annotation });
+
+		const moveArea = document.querySelector('[data-move-area]');
+		expect(moveArea).not.toBeNull();
+	});
+
+	it('renders an aria-live region for screen reader announcement', async () => {
+		render(AnnotationEditOverlay, { annotation });
+
+		const liveRegion = document.querySelector('[aria-live="polite"]');
+		expect(liveRegion).not.toBeNull();
+	});
+
+	it('SVG root has tabindex="0" so it can receive keyboard focus', async () => {
+		render(AnnotationEditOverlay, { annotation });
+
+		const svg = document.querySelector('svg[role="application"]');
+		expect(svg).not.toBeNull();
+		expect(svg!.getAttribute('tabindex')).toBe('0');
+	});
+});