Add compiled paper PDF, regenerated insights report, fix .gitignore

- arxiv/main.pdf: compiled academic paper (195 KB) via tectonic
  No specsmith/SEAL references; 4-model validation; pre-registration
  via public repo URL
- results/oea_insights_report.pdf: refreshed 10-page insights report
- .gitignore: add !arxiv/main.pdf and !arxiv/figures/ exceptions so
  compiled paper and figures are tracked as release artifacts

Co-Authored-By: Oz <oz-agent@warp.dev>

Author: tbitcs

.gitignore

@@ -28,7 +28,9 @@ venv/
 *.synctex.gz
 *.toc
 *.pk
-arxiv/main.pdf
+# arxiv/main.pdf and figures are committed as release artifacts
+!arxiv/main.pdf
+!arxiv/figures/
 
 # Research outputs — exclude generated run artifacts but keep committed experiment results
 # The primary results (pilot CSVs + summary_metrics.json) are committed directly.