docs(home): add a Downloads section listing every product's PDF / EPUB

Each product (Viewer / CLI / VFM / Themes / Reference / Cookbook) now
ships PDF and EPUB built by Vivliostyle CLI from the same Markdown
sources, but the home page didn't expose them as a coherent list —
only per-product slug pages had a sidebar download widget.

Add an H2 "Vivliostyle CLI生成物のダウンロード" / "Downloads (built by
Vivliostyle CLI)" right after the VFM Features Demo, with a 6-row
table linking each product to its PDF and EPUB. Order matches the
sidebar accordion: Product 4 items → Reference → Cookbook.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: ogwata

content/en/index.md

@@ -53,3 +53,16 @@ This demonstrates VFM's {Ruby|ルビ} support.
 ### Section Attribution
 
 Sections are automatically wrapped with appropriate IDs for CSS styling.
+
+## Downloads (built by Vivliostyle CLI)
+
+Every product's documentation on this site is generated from the same Markdown source as **PDF / EPUB** with Vivliostyle CLI ([Single Source, Multi Output](#ssmo)).
+
+| Product | PDF | EPUB |
+|---|---|---|
+| [Vivliostyle Viewer](/en/viewer/) | [PDF](/downloads/vivliostyle-viewer-en.pdf) | [EPUB](/downloads/vivliostyle-viewer-en.epub) |
+| [Vivliostyle CLI](/en/cli/) | [PDF](/downloads/vivliostyle-cli-en.pdf) | [EPUB](/downloads/vivliostyle-cli-en.epub) |
+| [VFM](/en/vfm/) | [PDF](/downloads/vfm-en.pdf) | [EPUB](/downloads/vfm-en.epub) |
+| [Vivliostyle Themes](/en/themes/) | [PDF](/downloads/vivliostyle-themes-en.pdf) | [EPUB](/downloads/vivliostyle-themes-en.epub) |
+| [Reference](/en/reference/) | [PDF](/downloads/vivliostyle-reference-en.pdf) | [EPUB](/downloads/vivliostyle-reference-en.epub) |
+| [Cookbook](/en/cookbook/) | [PDF](/downloads/vivliostyle-cookbook-en.pdf) | [EPUB](/downloads/vivliostyle-cookbook-en.epub) |

content/ja/index.md

@@ -53,3 +53,16 @@ VFMの{漢字|かんじ}サポートをデモンストレーションしてい
 ### セクション属性
 
 セクションはCSSスタイリング用の適切なIDで自動的にラップされます。
+
+## Vivliostyle CLI生成物のダウンロード
+
+このサイトの各プロダクトのドキュメントは、同じ Markdown ソースから Vivliostyle CLI で **PDF / EPUB** として生成しています（[Single Source, Multi Output](#ssmo)）。
+
+| プロダクト | PDF | EPUB |
+|---|---|---|
+| [Vivliostyle Viewer](/ja/viewer/) | [PDF](/downloads/vivliostyle-viewer-ja.pdf) | [EPUB](/downloads/vivliostyle-viewer-ja.epub) |
+| [Vivliostyle CLI](/ja/cli/) | [PDF](/downloads/vivliostyle-cli-ja.pdf) | [EPUB](/downloads/vivliostyle-cli-ja.epub) |
+| [VFM](/ja/vfm/) | [PDF](/downloads/vfm-ja.pdf) | [EPUB](/downloads/vfm-ja.epub) |
+| [Vivliostyle Themes](/ja/themes/) | [PDF](/downloads/vivliostyle-themes-ja.pdf) | [EPUB](/downloads/vivliostyle-themes-ja.epub) |
+| [リファレンス](/ja/reference/) | [PDF](/downloads/vivliostyle-reference-ja.pdf) | [EPUB](/downloads/vivliostyle-reference-ja.epub) |
+| [活用ガイド](/ja/cookbook/) | [PDF](/downloads/vivliostyle-cookbook-ja.pdf) | [EPUB](/downloads/vivliostyle-cookbook-ja.epub) |