docs(blueprint): article-class restructure, narrative, examples, conclusion

[cameronfreer]

Summary

Substantive expansion of the blueprint document: switches the print build from report to article class with a tighter layout, adds narrative framing and notation conventions, adds proof sketches and a Beta-Bernoulli example, and adds a conclusion / future-work chapter. All changes are confined to blueprint/; no Lean code is touched.

Commits (oldest first)

Commit	Scope
916053f9 — docs(blueprint): Switch to article class and restructure chapters	print.tex: report → article, tighter margins, compact title + abstract + ToC; chapter→section remap in macros/print.tex (print-only). Chapter renames: "Easy Directions" → "Elementary Implications", "Common Ending" → "Shared Final Step", "Main Theorem" → "The de Finetti–Ryll-Nardzewski Equivalence".
b0e90ab0 — docs(blueprint): Add narrative, notation section, and references	Expanded Introduction; "Setting and conventions" paragraph; "Terminology" note (contractable vs spreadable); "Contributions" paragraph (43,500 lines, 112 files); transitions between theorem blocks; new references.bib (7 entries) wired into print.tex.
bf3ebe73 — docs(blueprint): Add proof sketches, comparison table, and example	Route comparison table (key tool, extra assumptions, line count); Beta-Bernoulli urn example after core definitions; "Key idea" paragraphs for each of the three routes (martingale, L², Koopman); booktabs package for table formatting.
0076e5b6 — docs(blueprint): Add conclusion, future work, and notation polish	New "Conclusion and Future Work" chapter (upstreaming, partial exchangeability, parametric families); notation consistency pass (L², en-dash, i.i.d.\ spacing); chapter→section restructuring resolves the prior page-6 orphan issue.

Files changed

• blueprint/src/content.tex — narrative additions, proof sketches, table, example, conclusion (the bulk of the diff)
• blueprint/src/print.tex — article-class switch, ToC/abstract/bibliography wiring, booktabs
• blueprint/src/macros/print.tex — chapter→section remap for print-only build
• blueprint/src/references.bib — new file, 7 bib entries

No Lean files touched; no impact on lake build, axioms, or sorries.

Rebase note

This branch was originally cut from aec253b6 (pre-bump base) and does not yet contain the v4.30.0-rc2 toolchain bump (PR #17). Since all changes are confined to blueprint/src/ and the bump did not touch that subtree, a rebase onto current main should be conflict-free; alternatively merge resolves with no Lean-side concerns. Recommend rebase to keep history linear:

git fetch origin main
git rebase origin/main blueprint-docs

Test plan

• blueprint/src/ builds with latexmk / leanblueprint against current main after rebase.
• PDF (blueprint/print/print.pdf) renders with the new ToC, sections, and bibliography.
• Web build (blueprint/web/) still generates correctly.