Add arXiv-ready LaTeX build of the introspection note

[bamdadd]

Turns the flagship note into an arXiv-submittable paper.

What's here

• docs/note.tex — single-column article converted from docs/note.md.
• docs/note.pdf — compiled output (5 pages, pdflatex).
• docs/Makefile — make rebuilds the PDF (runs pdflatex twice); make clean clears aux files.
• docs/arxiv-submission.md — cs.LG endorsement-request draft + submission checklist (categories cs.LG/cs.CL, license, author metadata). Prep only.

Fidelity

• Embeds the real results/scaling_trend_k2.png (markers only, no fitted trend line) plus the size-ladder and 32B three-way tables.
• All numbers track the live RESULTS.md: size ladder base/instruct 0/216 throughout, code-instruct 0/216 (7B) / 1/216 (14B) / 5/216 (32B); 32B three-way CIs and affirmative/coherent rates verified against RESULTS.md. Total spend corrected to ~$23 ($6.6 GPU + ~$16 judge) to match RESULTS.md, where the source note.md still read $20.
• Honest-negative framing preserved verbatim in sense: null across the grid with one marginal above-chance cell (Coder-32B, 5/216) that does not survive its size ladder; conjunction of code-post-training and ~32B scale, not a main effect of either; no inferential trend test; the earlier fine-tune-not-scale framing is retracted.

Rebuild

cd docs && make

arXiv submission itself is deliberately not done here — it awaits an explicit go.