🐛 End RL episodes at the hard pass horizon

[flowerthrower]

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Description

Treat exhaustion of PredictorEnv.max_steps as a terminal outcome rather than
a time-limit truncation.

Stable-Baselines3 bootstraps Gymnasium truncations with the critic value of the
terminal observation. The configured pass limit is the hard compilation and
deployment horizon, so continuation beyond it is unreachable. This change
retains the zero reward but returns terminated=True and truncated=False when
a non-termination action consumes the final slot. Pass failures remain
truncations.

AI assistance was used to inspect the environment and Stable-Baselines3 rollout
semantics and to prepare this focused patch.

Checklist

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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