Stop consuming uniform clearing prices in the autopilot

[jmg-duarte]

Description

The autopilot no longer needs per-solution uniform clearing prices: scoring uses auction-level native prices, and on-chain settlement verification reads UCPs straight from the calldata. This PR removes UCPs from the autopilot's domain model and persistence path while keeping the wire format intact, so the change is safe under a rolling k8s deploy.

Changes

• Drop prices from the autopilot's domain Solution (field, constructor arg, and prices() getter).
• Remove SolutionError::InvalidPrice and its invalid_price metric label — price validation is no longer performed when ingesting a /solve response.
• Persist empty arrays into proposed_solutions.price_tokens / price_values. The NOT NULL columns are retained for now (an empty array still satisfies the constraint); they can be dropped in a follow-up.
• Make the autopilot tolerant of drivers that omit clearingPrices: add #[serde(default)] to the deserializer and emit a debug! log when a driver still sends a non-empty map, so we can chase down stragglers before fully removing the field.
• Leave the driver emitting clearingPrices on /solve responses (with a deprecation comment) so autopilots running the previous code can still deserialize during the rolling deploy.
• Mark clearingPrices as deprecated: true in the driver /solve response schema and in the orderbook solver_competition_v2 schema, with a note explaining that recent autopilots will return it empty.

A follow-up PR will remove the driver-side field, the deprecation log, and (optionally) drop the now-unused proposed_solutions.price_tokens / price_values columns.

How to test

1. cargo nextest run -p autopilot -p driver — unit tests, including winner_selection tests updated to construct solutions without prices.
2. Hit solver_competition_v2 for an auction produced by the new autopilot and confirm clearingPrices is {}; for an auction produced before the change it remains populated.

Staging

Ran in staging with these orders:

• https://dev.explorer.cow.fi/orders/0x34ce7c3c6b4c762663d087b2c6ffba30fc966d9bf98039eee98ad1722e79805309fbad1ea29c36dfe4f8f7baa87c5edf85e0d9f369fc62fe
• https://dev.explorer.cow.fi/orders/0xaf624d224a01e7ecaff3d0be2a04a1e073090f3e9cfdad220cea741748f3e83109fbad1ea29c36dfe4f8f7baa87c5edf85e0d9f369fc66f9

Logs:

• https://victorialogs.dev.cow.fi/goto/eflbzd4yhhy4ga?orgId=1
• https://victorialogs.dev.cow.fi/goto/bflc0jc6wa874b?orgId=1

[github-actions]

Reminder: Please consider backward compatibility when modifying the API specification.
If breaking changes are unavoidable, ensure:

• You explicitly pointed out breaking changes.
• You communicate the changes to affected teams (at least Frontend team and SAFE team).
• You provide proper versioning and migration mechanisms.

---

Caused by:

• crates/driver/openapi.yml
• crates/orderbook/openapi.yml

[gemini-code-assist]

Code Review

This pull request deprecates and removes the use of uniform clearing prices across the autopilot and driver components. Key changes include removing the prices field from the Solution domain model, updating the persistence layer to store empty price vectors, and marking clearing_prices as deprecated in the OpenAPI specifications and DTOs to maintain backward compatibility during rolling deployments. No critical issues found; I have no feedback to provide.