P2-04: coalesce facade autosaves

tests/facade.test.ts

@@ -2,7 +2,7 @@ import { test } from 'node:test'
 import assert from 'node:assert/strict'
 import { createMockFacade } from '../src/facade/mockFacade'
 import { PROJECT_SCHEMA_MIGRATIONS, PROJECT_SCHEMA_SQL, PROJECT_SCHEMA_VERSION } from '../src/facade/projectSchema'
-import { PersistenceWriteQueue } from '../src/facade/projectStore'
+import { PersistenceWriteQueue, ProjectAutosaveScheduler } from '../src/facade/projectStore'
 
 test('facade exposes a stable initial document projection', () => {
   const facade = createMockFacade()
@@ -42,6 +42,20 @@ test('persistence writes are serialized and continue after a failed write', asyn
   assert.equal(results[2].status, 'fulfilled')
 })
 
+test('autosave scheduler coalesces idle document changes and flushes the latest version', async () => {
+  const savedVersions: number[] = []
+  const scheduler = new ProjectAutosaveScheduler(async (document) => { savedVersions.push(document.version); return { documentId: document.id, documentVersion: document.version, persistedAt: Date.now(), mode: 'sqlite-memory' } }, 5)
+  const document = (version: number) => ({ id: 'doc', label: 'Autosave', version, dirty: true, readOnly: false, units: 'mm', tree: [] })
+  scheduler.schedule(document(1))
+  scheduler.schedule(document(2))
+  await new Promise((resolve) => setTimeout(resolve, 15))
+  assert.deepEqual(savedVersions, [2])
+  scheduler.schedule(document(3))
+  const result = await scheduler.flush()
+  assert.equal(result?.documentVersion, 3)
+  scheduler.cancel()
+})
+
 test('workbench and selection changes are event driven', () => {
   const facade = createMockFacade()
   const events: string[] = []