Adds ib_gradient_direction CUDA kernel that fires when population variance
of Q(a) across b0 actions falls below min_var=0.01, pushing each Q(a) away
from mean_q. Piggybacked on cql_d_adv_logits / cql_d_value_logits (same
atomicAdd path as F5 barrier). ib_weight = 0.05 × (1−health) → zero-op when
network is healthy (health≈1). Wired inside apply_cql_gradient immediately
after the F5 barrier launch, flows through the existing CQL SAXPY + backward.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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