[Service] /checkout/quote and /checkout/orders disagree on a priced-but-untitled product

[vedanshujain]

/checkout/quote and /checkout/orders disagree about a priced-but-untitled product:

• quote checks the price only (packages/service/src/routes/orders.ts), so it answers 200;
• place goes through createOrderFromCart, whose null-title guard rejects, so it 409s.

A buyer can therefore be quoted a total for a cart that cannot be placed. Nothing pins the
asymmetry in either direction, so it is not currently a decision — it is an accident.

Two things to settle when this is picked up:

1. Which behaviour is right — quote should reject too (fail early, consistent), or place should
   tolerate a missing title (which contradicts the order-line snapshot invariant, so probably not).
2. Pin it with a test either way, so the two endpoints cannot drift again.

Related: the untested title half of the place-side guard is tracked separately.

Source: plans/one-home-per-field.md §7.0, §9.5, §9.7.