feat: add isolated memory spaces

tests/identity-db.test.ts

@@ -34,6 +34,58 @@ describe('IdentityDB topic and fact writes', () => {
     expect(topics).toHaveLength(1);
   });
 
+  it('keeps same normalized topic names isolated across spaces', async () => {
+    const alpha = await db.upsertTopic({
+      name: 'TypeScript',
+      category: 'entity',
+      granularity: 'concrete',
+      spaceName: 'A',
+    });
+
+    const beta = await db.upsertTopic({
+      name: 'TypeScript',
+      category: 'entity',
+      granularity: 'concrete',
+      spaceName: 'B',
+    });
+
+    expect(beta.id).not.toBe(alpha.id);
+
+    const alphaTopics = await db.listTopics({ includeFacts: false, spaceName: 'A' });
+    const betaTopics = await db.listTopics({ includeFacts: false, spaceName: 'B' });
+    const defaultTopics = await db.listTopics({ includeFacts: false });
+
+    expect(alphaTopics.map((topic) => topic.name)).toEqual(['TypeScript']);
+    expect(betaTopics.map((topic) => topic.name)).toEqual(['TypeScript']);
+    expect(defaultTopics).toHaveLength(0);
+  });
+
+  it('keeps alias resolution scoped to the requested space', async () => {
+    await db.upsertTopic({
+      name: 'TypeScript',
+      category: 'entity',
+      granularity: 'concrete',
+      spaceName: 'A',
+    });
+    await db.upsertTopic({
+      name: 'TeamSpeak',
+      category: 'entity',
+      granularity: 'concrete',
+      spaceName: 'B',
+    });
+
+    await db.addTopicAlias('TypeScript', 'TS', { spaceName: 'A' });
+    await db.addTopicAlias('TeamSpeak', 'TS', { spaceName: 'B' });
+
+    const alphaResolved = await db.resolveTopic('ts', { spaceName: 'A' });
+    const betaResolved = await db.resolveTopic('ts', { spaceName: 'B' });
+    const defaultResolved = await db.resolveTopic('ts');
+
+    expect(alphaResolved?.name).toBe('TypeScript');
+    expect(betaResolved?.name).toBe('TeamSpeak');
+    expect(defaultResolved).toBeNull();
+  });
+
   it('adds one fact that links multiple topics', async () => {
     const fact = await db.addFact({
       statement: 'I have worked with TypeScript since 2025.',