Linear magnitude ratios in reward_component_mag_ratio_compute_kernel
amplified popart's intrinsic O(100) magnitude over the other 5
components' O(0.1-2) magnitudes, causing controller to saturate
w_pop toward MAX_WEIGHT regardless of actual signal quality.
Replaced with z-score: z[c] = mag[c] / max(sqrt(var[c]), EPS_DIV).
6 new ISV slots [361..367) for per-component variance EMAs computed
via Welford's online algorithm in extended popart_component_ema_kernel
and reward_component_ema_kernel.
Atomic per feedback_no_partial_refactor: slot allocation +
state-reset registry + 2 producer kernels + canary signature +
launcher Pearls A+D + tests.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
b3b4d02789