⚡ Use compact scalar RL observations

[flowerthrower]

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Description

Replaces the discrete num_qubits and depth RL observations with one-element float32 values in [0, 1]. Qubit count is scaled linearly and capped at 127; depth is log1p-scaled and capped at 999,999.

This prevents Stable-Baselines3 from expanding those values into large one-hot vectors and reduces the flattened policy input from 1,000,162 features to 36. Existing RL models must be retrained, and direct PredictorEnv observation consumers must handle the new array values.

This stacked PR depends on #760 and contains no phase/deadline observations, GNN changes, or local diagnostic tooling. Validated with uvx nox -s lint, the RL helper/tracer tests (7 passed), and an observation-schema smoke check.

Checklist

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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