feat(db): conversations.findOrCreateForSpace for the ambient companion

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/db/conversations_companion.test.js

@@ -0,0 +1,26 @@
+import { describe, it, expect, beforeAll } from 'vitest';
+import { pool } from '../../lib/db/pool.js';
+import { resetDb } from '../helpers/db.js';
+import { migrateUp } from '../../lib/db/migrate.js';
+import * as conversations from '../../lib/db/repos/conversations.js';
+
+const ACTOR = { kind: 'user', id: null };
+let spaceId, agentId;
+
+beforeAll(async () => {
+  await resetDb(); await migrateUp();
+  ({ rows: [{ id: spaceId }] } = await pool.query(
+    `INSERT INTO spaces(slug,name) VALUES('s','S') RETURNING id`));
+  ({ rows: [{ id: agentId }] } = await pool.query(
+    `SELECT id FROM agents WHERE slug='companion'`));
+});
+
+describe('findOrCreateForSpace', () => {
+  it('creates once then returns the same row', async () => {
+    const a = await conversations.findOrCreateForSpace(spaceId, agentId, ACTOR);
+    const b = await conversations.findOrCreateForSpace(spaceId, agentId, ACTOR);
+    expect(a.id).toBe(b.id);
+    expect(a.space_id).toBe(spaceId);
+    expect(a.agent_id).toBe(agentId);
+  });
+});