Add workshop preprint scaffolding (#11)

First scaffold of the workshop preprint draft (issue #11). Compiles
with generic pdflatex/latexmk against the included bibliography.

Structure:
    paper/
      main.tex                         article-class root
      bibliography.bib                 12 references (HELM/MMLU/BigBench,
                                        red-teaming, CheckList, XSTest,
                                        sycophancy, RewardBench, plus
                                        Olah/Elhage interpretability)
      sections/01-07                   intro / related work / method /
                                        implementation / validation /
                                        limitations / future work
      appendix/A-C                     prompts / transcripts / code
      figures/                         empty (.gitkeep)
      README.md                        build instructions, status,
                                        outstanding work, arXiv flow

Content seeded from existing repo material (method.md, taxonomy.md,
related-work.md, case analysis.md files, README.md) so the structure
and argument flow are in place. Places that need original authorial
writing or numbers from runs that haven't been executed yet are
flagged with \todo{...} blocks; these render in red in the compiled
PDF and are easy to grep for in source.

The validation section reports the Case 3 headline (regex 0.20 vs.
LLM-judge 0.73, +0.53 delta) but explicitly annotates that it is a
single-run point estimate and that distribution stats (#10) and
cross-family judge agreement (#8) are pending the empirical work.

Root README.md Citation section now points to paper/ and notes that
the arXiv ID will replace the GitHub URL once submitted. No arXiv ID
yet because submission requires the work outlined in paper/README.md
to land first.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>