Bound habit day and calendar reads to requested history

src/habits/performance.test.ts

@@ -0,0 +1,23 @@
+import { expect, test } from 'bun:test';
+import { fixture } from './test-fixture';
+import { HabitService } from './service';
+import { publicUser } from '../auth';
+import { users } from '../db/schema';
+import { eq } from 'drizzle-orm';
+
+test('single-day reads load only the selected latest snapshot and its tasks', async () => {
+  const f = fixture();
+  try {
+    const habit = await f.json('/habits', 'POST', { name: 'Tasks', method: 'tasks', tasks: [{name:'Read'}] }, 201);
+    f.setTime('2027-09-04T12:00:00Z');
+    await f.json('/today');
+    const logs: string[] = [];
+    (f.db as any).session.logger = { logQuery(query: string) { logs.push(query); } };
+    const service = new HabitService(f.db, publicUser(f.db.select().from(users).where(eq(users.id,'alice')).get()!), Date.parse('2027-09-04T12:00:00Z'));
+    const day = service.day(habit.id, '2027-09-04');
+    expect(day.tasks).toHaveLength(1);
+    expect((service as any).recordsCache.get(habit.id).size).toBe(1);
+    expect((service as any).occurrencesCache.get(habit.id).size).toBe(1);
+    expect(logs.find(query => query.includes('task_occurrences'))).toContain('"habit_days"."date" >=');
+  } finally { f.close(); }
+});