fix(gemma4): exact router scalar and fp32 reference routing for MoE parity (#3456)

* fix(gemma4): exact router scalar and fp32 reference routing for MoE parity

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* ci(minimax_m3): set ep32pp4 job time to 1 hour

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* test(gemma4): run 26b moe robustness phases process-isolated

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* test(gemma4): disable unstable source-load logit parity for 26b moe

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* test(ci): allow gemma4 26b moe to opt out of source-load parity

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 5 <noreply@anthropic.com>