giant predict/rollout rebuilt models straight from ckpt["model_config"] with
no way to change sampling-only keys (e.g. stage2_model.n_sec.stop_sampling)
without retraining. Adds config_overrides to load_for_inference, validated
against giant.config.INFERENCE_OVERRIDES so a typo or shape-bearing key
raises CheckpointCompatibilityError up front instead of an opaque
load_state_dict mismatch. Wired as a repeatable --set dotted.path=value on
both CLI commands, recorded in the rollout YAML sidecar, and surfaced in
`giant model summary`'s output.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>