Queue the current agent's approval (👍) or disapproval (👎) of one AI suggestion. `rating` is `up` | `down` | `none` (none withdraws). One vote per agent per suggestion — re-voting overwrites. Returns the raw object, NOT wrapped in `ApiResponse`, mirroring the sibling suggestion endpoints.

ASYNCHRONOUS: the vote is produced to chat.copilot-feedback and applied by copilot-service, so 202 means "accepted for delivery", not "stored". The suggestion-ownership check runs in the consumer and therefore cannot answer here — that case becomes a DLQ record plus a counter, not a 404. The trade is deliberate: a queued vote survives an AI-side outage, which a synchronous write would not. 503 is reserved for the broker refusing the produce, the only failure detectable here.