docs: add arXiv paper on ArcheFlow architecture

LaTeX paper describing the archetypal role system, PDCA quality cycles,
shadow detection framework, attention filters, convergence detection,
and effectiveness scoring. References Lu et al. 2026 (Assistant Axis)
for persona stability grounding.

.gitignore

@@ -8,3 +8,11 @@ Thumbs.db
 # Editor
 *.swp
 *~
+# Paper build artifacts
+paper/*.aux
+paper/*.bbl
+paper/*.blg
+paper/*.log
+paper/*.out
+paper/*.pdf
+paper/*.toc