Run Frozen Multi-Season Backtest

Replay the persisted recursive states for 2023-24 through 2025-26 without refitting the player or context models:

uv run nba-run-frozen-multiseason-backtest --seasons 2023-24 2024-25 2025-26

The command reads each target-season player-prior vector and the immediately preceding completed context state from the model's immutable 2025-26 artifact. It writes an independently versioned report under:

artifacts/models/frozen_multiseason_backtest/2023-24_to_2025-26/

The report includes regular-season per-possession, eligible-game, full-game, team NetRtg, and Pythagorean-win metrics for each replay season, plus pooled summaries. Historical playoff possession partitions have not yet been materialized for 2023-24 and 2024-25, so playoff results are intentionally out of scope for this common comparison.