Freeze an Order Item's Recipe at order time

Price was already snapshotted per Order Item so later menu changes
don't rewrite history, but the Recipe (Step list) wasn't: advancing an
Order Item looked up its next Step from the live menuItemSteps table,
so an operator editing a Menu Item's Recipe mid-cook could silently
reshape an Order already in flight (different Machine Tag, duration,
or Step order than what the customer paid for).

Adds order_item_steps as a per-Order-Item copy of the Recipe, taken at
placement time; placeOrder, advanceOrderItemStep, and getOrderStatus
now all read from that snapshot instead of the live menu. Recorded as
docs/adr/0005 and added Recipe as a formal CONTEXT.md term.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/ordering.test.ts

@@ -1,3 +1,4 @@
+import { and, eq } from 'drizzle-orm'
 import {
   afterAll,
   afterEach,
@@ -38,6 +39,7 @@ beforeEach(() => {
 // between tests instead of leaking a busy state into the next one.
 afterEach(async () => {
   await testDb.db.delete(schema.preparationStepInstances)
+  await testDb.db.delete(schema.orderItemSteps)
   await testDb.db.delete(schema.orderItems)
   await testDb.db.delete(schema.orders)
 })
@@ -335,6 +337,53 @@ describe('advancing steps and pickup', () => {
   })
 })
 
+describe('recipe snapshot', () => {
+  it("keeps an Order Item on the Recipe as it existed at order time, even if the Menu Item's live Recipe is edited afterwards", async () => {
+    const order = await placeGuestOrder([
+      { menuItemId: seed.menuItems.burger.id },
+    ])
+
+    const burgerSecondStepEdit = and(
+      eq(schema.menuItemSteps.menuItemId, seed.menuItems.burger.id),
+      eq(schema.menuItemSteps.sequence, 2),
+    )
+    // Edit the live Recipe after the Order was placed: swap the burger's
+    // second Step to a different Machine Tag and duration.
+    await testDb.db
+      .update(schema.menuItemSteps)
+      .set({
+        machineTagId: seed.machineTags.oven.id,
+        estimatedDurationSeconds: 999,
+      })
+      .where(burgerSecondStepEdit)
+
+    try {
+      const beforeAdvance = await getStatus(order)
+      const burgerItemId = beforeAdvance.items[0].id
+      const pendingStep = beforeAdvance.items[0].steps[1]
+      expect(pendingStep.status).toBe('pending')
+      expect(pendingStep.machineTag).toBe('assembly')
+      expect(pendingStep.estimatedDurationSeconds).toBe(90)
+
+      await ordering.advanceOrderItemStep(testDb.db, burgerItemId)
+
+      const afterAdvance = await getStatus(order)
+      const secondStep = afterAdvance.items[0].steps[1]
+      expect(secondStep.status).toBe('in_progress')
+      expect(secondStep.machineTag).toBe('assembly')
+      expect(secondStep.estimatedDurationSeconds).toBe(90)
+    } finally {
+      await testDb.db
+        .update(schema.menuItemSteps)
+        .set({
+          machineTagId: seed.machineTags.assembly.id,
+          estimatedDurationSeconds: 90,
+        })
+        .where(burgerSecondStepEdit)
+    }
+  })
+})
+
 describe('access control', () => {
   it('refuses to show order status to someone without the access token', async () => {
     const order = await placeGuestOrder([