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/dimensionValidation.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, it, vi } from 'vitest';
+
+vi.mock('@/services/database/sqlite-client', () => ({
+  getSQLiteClient: vi.fn(),
+}));
+
+import { getSQLiteClient } from '@/services/database/sqlite-client';
+import { formatUnknownDimensionsError, getUnknownDimensions } from '@/services/database/dimensionValidation';
+
+describe('dimensionValidation', () => {
+  it('returns dimensions missing from the canonical dimensions table', () => {
+    vi.mocked(getSQLiteClient).mockReturnValue({
+      query: vi.fn().mockReturnValue({
+        rows: [{ name: 'ra-h' }, { name: 'ai' }],
+      }),
+    } as unknown as ReturnType<typeof getSQLiteClient>);
+
+    expect(getUnknownDimensions(['ra-h', 'Building RA-H — Personal Knowledge Graph', 'ai'])).toEqual([
+      'Building RA-H — Personal Knowledge Graph',
+    ]);
+  });
+
+  it('formats a clear error for unknown dimensions', () => {
+    expect(formatUnknownDimensionsError(['Building RA-H — Personal Knowledge Graph']))
+      .toBe('Unknown dimension: "Building RA-H — Personal Knowledge Graph". Create it first or use an existing dimension.');
+  });
+});