Add `contrarian_active` int parameter to `experience_action_select` kernel.
When non-zero, a `q_sign = -1.0f` multiplier is applied to Q values across
all 4 branches (direction/magnitude/order/urgency) before Boltzmann softmax,
converting argmax-favoring sampling to argmin-favoring without touching
temperature, epsilon, conviction filter, masking, or sampling logic.
When zero, q_sign = +1.0f — behavior is bit-identical to before.
Wire: GpuExperienceCollector gains `contrarian_active_cache: u8` field plus
`set_contrarian_active()` / `contrarian_active()` accessors. The flag is
appended as the last arg at the action_select launch site. training_loop.rs
propagates `self.contrarian_active` to the collector immediately after the
D7 Part A state machine updates.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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