feat: enhance PDF comparison with new change types and zoom functionality

- Added support for 'moved' and 'style-changed' change types in PDF comparison.
- Implemented category filters for changes, allowing users to filter by text, images, headers, annotations, formatting, and background.
- Introduced zoom functionality with buttons for zooming in, out, and resetting to default.
- Updated UI to reflect new change types and categories, including visual indicators for moved and style-changed items.
- Enhanced summary display to include counts for moved and style-changed changes.
- Refactored rendering logic to accommodate zoom levels and improve performance.
- Added tests for new change detection features and category assignments.

src/js/compare/engine/compare.worker.ts

@@ -0,0 +1,77 @@
+import { diffTextRuns } from './diff-text-runs.ts';
+import { pairPages } from './pair-pages.ts';
+import type {
+  CompareTextItem,
+  ComparePageSignature,
+  ComparePagePair,
+  ComparePageResult,
+  CompareChangeSummary,
+  CompareTextChange,
+} from '../types.ts';
+
+interface DiffMessage {
+  type: 'diff';
+  id: number;
+  beforeItems: CompareTextItem[];
+  afterItems: CompareTextItem[];
+}
+
+interface PairMessage {
+  type: 'pair';
+  id: number;
+  leftPages: ComparePageSignature[];
+  rightPages: ComparePageSignature[];
+}
+
+type WorkerMessage = DiffMessage | PairMessage;
+
+interface DiffResult {
+  type: 'diff';
+  id: number;
+  changes: CompareTextChange[];
+  summary: CompareChangeSummary;
+}
+
+interface PairResult {
+  type: 'pair';
+  id: number;
+  pairs: ComparePagePair[];
+}
+
+interface ErrorResult {
+  type: 'error';
+  id: number;
+  message: string;
+}
+
+type WorkerResult = DiffResult | PairResult | ErrorResult;
+
+self.onmessage = function (e: MessageEvent<WorkerMessage>) {
+  const msg = e.data;
+  try {
+    if (msg.type === 'diff') {
+      const { changes, summary } = diffTextRuns(
+        msg.beforeItems,
+        msg.afterItems
+      );
+      const result: DiffResult = {
+        type: 'diff',
+        id: msg.id,
+        changes,
+        summary,
+      };
+      self.postMessage(result);
+    } else if (msg.type === 'pair') {
+      const pairs = pairPages(msg.leftPages, msg.rightPages);
+      const result: PairResult = { type: 'pair', id: msg.id, pairs };
+      self.postMessage(result);
+    }
+  } catch (err) {
+    const result: ErrorResult = {
+      type: 'error',
+      id: msg.id,
+      message: err instanceof Error ? err.message : String(err),
+    };
+    self.postMessage(result);
+  }
+};