fix: port search and dimension safety guardrails

- enforce canonical dimensions across app and MCP surfaces
- prioritize title-first node search in UI and query tools
- add regression tests for ranking and dimension validation

tests/unit/database/searchRanking.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, it } from 'vitest';
+
+import { scoreNodeSearchMatch } from '@/services/database/searchRanking';
+
+describe('scoreNodeSearchMatch', () => {
+  it('strongly prefers the closest title match for hub-node queries', () => {
+    const query = 'building ra-h';
+
+    const hubScore = scoreNodeSearchMatch({
+      title: 'Building RA-H — Personal Knowledge Graph',
+      description: 'Brad project hub',
+      source: '',
+      updated_at: '2026-03-23T00:00:00.000Z',
+    }, query);
+
+    const broadScore = scoreNodeSearchMatch({
+      title: 'the ra-h project',
+      description: 'Foundational project document for RA-H',
+      source: '',
+      updated_at: '2026-03-23T00:00:00.000Z',
+    }, query);
+
+    expect(hubScore).toBeGreaterThan(broadScore);
+  });
+});