refactor(transcription): extract useBlockAutoSave and useBlockDragDrop from TranscriptionEditView (#199)

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

frontend/src/lib/hooks/__tests__/useBlockDragDrop.svelte.test.ts

@@ -0,0 +1,79 @@
+import { describe, it, expect, vi } from 'vitest';
+import { createBlockDragDrop } from '../useBlockDragDrop.svelte';
+import type { TranscriptionBlockData } from '$lib/types';
+
+function makeBlock(id: string, sortOrder: number): TranscriptionBlockData {
+	return {
+		id,
+		annotationId: `ann-${id}`,
+		documentId: 'doc-1',
+		text: '',
+		label: null,
+		sortOrder,
+		version: 1,
+		source: 'MANUAL',
+		reviewed: false
+	};
+}
+
+describe('createBlockDragDrop', () => {
+	it('initial state — no drag in progress', () => {
+		const dd = createBlockDragDrop({ getSortedBlocks: () => [], onReorder: vi.fn() });
+		expect(dd.draggedBlockId).toBeNull();
+		expect(dd.dropTargetIdx).toBeNull();
+		expect(dd.dragOffsetY).toBe(0);
+	});
+
+	it('handleGripDown sets draggedBlockId when grip is hit', () => {
+		const dd = createBlockDragDrop({ getSortedBlocks: () => [], onReorder: vi.fn() });
+		const grip = document.createElement('div');
+		grip.setAttribute('data-drag-handle', '');
+		const wrapper = document.createElement('div');
+		wrapper.setAttribute('data-block-wrapper', '');
+		wrapper.appendChild(grip);
+		document.body.appendChild(wrapper);
+
+		const e = new PointerEvent('pointerdown', { clientY: 100, cancelable: true, bubbles: true });
+		Object.defineProperty(e, 'target', { value: grip });
+		wrapper.setPointerCapture = vi.fn();
+
+		dd.handleGripDown(e as PointerEvent, 'block-1');
+		expect(dd.draggedBlockId).toBe('block-1');
+
+		document.body.removeChild(wrapper);
+	});
+
+	it('handlePointerUp without active drag is a no-op', () => {
+		const onReorder = vi.fn();
+		const dd = createBlockDragDrop({ getSortedBlocks: () => [], onReorder });
+		dd.handlePointerUp();
+		expect(onReorder).not.toHaveBeenCalled();
+	});
+
+	it('handlePointerUp with null dropTargetIdx does not call onReorder', () => {
+		const onReorder = vi.fn();
+		const blocks = [makeBlock('b1', 0), makeBlock('b2', 1)];
+		const dd = createBlockDragDrop({ getSortedBlocks: () => blocks, onReorder });
+
+		// Simulate a drag start without going through handleGripDown internals
+		// by checking that handlePointerUp without a drop target is a no-op for reorder
+		const grip = document.createElement('div');
+		grip.setAttribute('data-drag-handle', '');
+		const wrapper = document.createElement('div');
+		wrapper.setAttribute('data-block-wrapper', '');
+		wrapper.appendChild(grip);
+		document.body.appendChild(wrapper);
+		wrapper.setPointerCapture = vi.fn();
+
+		const downEvent = new PointerEvent('pointerdown', { clientY: 50, cancelable: true });
+		Object.defineProperty(downEvent, 'target', { value: grip });
+		dd.handleGripDown(downEvent as PointerEvent, 'b1');
+
+		// dropTargetIdx is still null (no pointer move happened)
+		dd.handlePointerUp();
+		expect(onReorder).not.toHaveBeenCalled();
+		expect(dd.draggedBlockId).toBeNull();
+
+		document.body.removeChild(wrapper);
+	});
+});