test(sync): implement test-strategy Phase 1-2 (pure unit/golden/property), +102 tests

Work through test-strategy-report.md, high-ROI no-refactor subset (no regen).

- R-Infra: vitest resolve.alias docmost-client -> packages/docmost-client/src
  (fixes the dist-vs-src coverage artifact: canonicalize 0% -> real)
- R-Cfg-1: export parseArgs + tests
- canonicalize: align family / comment.resolved kept / link non-default +
  fixpoint & docsCanonicallyEqual reflexive/symmetric properties (0 -> 100%)
- markdown-converter golden matrix: columns/embed/audio/pdf, drawio data-align
  rule, inline-mark matrix, textAlign, escaping idempotence, table sanitization
  (61 -> 79%)
- schema parse-closures via generateJSON (TextStyle/comment/mention/Highlight/Column)
- node-ops (immutability, table edge cases, makeFreshId property), transforms
  (setCalloutRange/insertMarkerAfter/commentsToFootnotes + renumber property)
- stabilize normalize-on-write fixpoint (0 -> 100%); diff coarse-fallback;
  client-utils; firstDivergence; corpus fixtures details/columns/mention
- 593 -> 695 green; build clean; corpus STABLE

Deferred (Phase 3-4, refactor-gated): pull/collab/client-REST/git-merge integration.

test/diff.test.ts

@@ -264,6 +264,24 @@ describe('diffDocs', () => {
       expect(result.summary).toEqual({ inserted: 0, deleted: 0, blocksChanged: 0 });
     });
 
+    it('still computes integrity (images/tables/callouts/footnotes) in the coarse-fallback branch', () => {
+      // Regression guard: integrity is computed BEFORE the try/catch, so a
+      // pathological pair that forces the fallback must NOT zero the integrity
+      // counts. The unknown node forces the precise path to throw (fellBack).
+      const oldDoc = doc(image(), callout(), table(), para('a [1]'), { type: '___nope' });
+      const newDoc = doc(image(), image(), table(), para('b [2] [3]'));
+      const result = diffDocs(oldDoc, newDoc);
+
+      // The fallback was taken...
+      expect(result.markdown).toContain('coarse block-level diff shown.');
+      // ...yet every integrity tuple is the real count, not [0,0].
+      expect(result.integrity.images).toEqual([1, 2]);
+      expect(result.integrity.callouts).toEqual([1, 0]);
+      expect(result.integrity.tables).toEqual([1, 1]);
+      // Footnote markers are counted from both docs even under the fallback.
+      expect(result.integrity.footnoteMarkers).toEqual([[1], [2, 3]]);
+    });
+
     it('reports both a deletion and an insertion in the fallback path', () => {
       const oldDoc = doc(para('old paragraph'), { type: '___nope' });
       const newDoc = doc(para('new paragraph'));