Refine training narrative and add AI use disclosure

[aadarwal]

Summary

• Replace the Section V-B training narrative with the revised motivation and description of the Run B evaluator loop.
• Preserve the Qwen3.6-35B-A3B, LoRA, GRPO, and Tinker citations.
• Retain the reward helper definitions and numbered reward branches as Eqs. (4a) and (4b).
• Add the author-provided AI use policy to the acknowledgments and retain the requested funding and laboratory acknowledgments.
• Refresh assets/pixcell-paper.pdf from the compiled manuscript.

Editorial repairs

• Apply only local punctuation, hyphenation, and grammatical repairs to the supplied text.
• Clarify cover representation as cover the representation space and see if as determine whether.
• Repair the incomplete acknowledgment construction as having been created or certified by them as all of which were created or certified by them.
• Add no unnecessary bibliography entries for the AI use disclosure.

Validation

• Compiled arxiv/main.tex with Tectonic.
• Visually inspected pages 12 through 15, including Eqs. (4a) and (4b), the table and section transitions, and the complete acknowledgment across its page break.
• Ran uv run pytest rl/track_a/tests/test_output_reward.py -q: 16 passed, 1 skipped.
• Confirmed there are no undefined citations or references in the LaTeX log.