Settlement & refund handling

[JSONbored]

Problem: No handling exists for partial loop completion, failed loops, or disputed results.

Area: gittensor economics

Proposal: Implement settlement logic covering: a loop that completes fully, one that's killed mid-run (per #4782's kill-switch semantics), and one that fails outright — each with a defined, consistent outcome for the customer's remaining allocation.

Deliverables:

• Settlement logic covering all three scenarios above, each producing a correct ledger entry (Rental ledger integration #4792).

Acceptance criteria:

• Each of the three scenarios produces the expected settlement outcome in a test run.

Boundaries:

• Blocked on Stake/payment → compute-time pricing #4790 and Third-party autonomy & security governance spec #4782.

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Part of #4778.

[linear-code]

JSO-3463