Miner grading and assignment

Miners submit candidate artifacts and signed operational evidence. Validators independently check the artifacts and evaluate held-out examples. A miner's own quality claim cannot set its grade or bypass acceptance thresholds.

The shared policy is implemented in zils/miner_grading.py. It checks comparable model/trainer/rubric/benchmark contexts, expires stale evidence, and separates qualification from customer work. The signed presence client is in zils/miner_presence.py; the queue miner can opt into reporting readiness.

Qualification, assignment, and model acceptance are different decisions. A successful qualification is not a customer model, a heartbeat is not proof of quality, and an accepted assignment does not guarantee a qualifying candidate. The policy's observation binding uses the uploaded artifact hash before calibration changes the checkpoint.

Run make check to exercise the shared policy and worker contracts. Hosted assignment, admission, database migrations, resource binding and qualification administration moved to the zils-platform operator guide. The closed Bittensor fleet's weight publication remains documented in testnet operation.