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.

vitest.config.ts

@@ -1,6 +1,25 @@
+import { fileURLToPath } from 'node:url';
+import path from 'node:path';
 import { defineConfig } from 'vitest/config';
 
+// R-Infra (test-strategy report §1/§5): tests that import from the package
+// barrel (`docmost-client`) otherwise resolve to the package `main` (the stale
+// compiled `dist/index.js`), so v8 coverage measures `src` while the tests run
+// against `dist`. `canonicalize.ts` in particular reads 0% despite 22 green
+// tests. Aliasing the barrel specifier to the package's `src/index.ts` makes
+// barrel-imported tests both run and be measured against `src`.
+const here = path.dirname(fileURLToPath(import.meta.url));
+const clientSrcBarrel = path.resolve(
+  here,
+  'packages/docmost-client/src/index.ts',
+);
+
 export default defineConfig({
+  resolve: {
+    alias: {
+      'docmost-client': clientSrcBarrel,
+    },
+  },
   test: {
     environment: 'node',
     include: ['test/**/*.test.ts'],