Build the missing calibration-report join

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Problem: Prediction records and realized outcomes are tracked independently with no aggregation function joining them into a real calibration report — a miner operator has no way to see their own prediction accuracy today, even though all the raw data exists.

Area: AMS / Miner

Proposal: Build the join between prediction records and realized outcomes, producing a real calibration report, and surface it through a CLI command.

Deliverables:

• A working calibration-report generator and a CLI command to view it.

Acceptance criteria:

• Running the new command against real prediction/outcome data produces an accurate accuracy report.

Scope note: this issue is limited to building a read-only calibration REPORT -- joining existing prediction records with existing realized outcomes and exposing the result via a CLI command. It must not modify the live scoring/calibration logic that feeds the actual gate; that stays maintainer-only.

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JSO-3509