fix: Jekyll設定をGitHub Pages標準構成に変更

- 複雑な依存関係を排除してシンプルな構成に
- theme: minima を使用
- GitHub Pages標準のgemのみ使用
- ビルド成功を優先した安定構成

docs/Gemfile

@@ -1,28 +1,15 @@
-# GitHub Pages用Gemfile
+# GitHub Pages用 - シンプル構成
 
 source "https://rubygems.org"
 
-# GitHub Pages（JekyllはGitHub Pagesに含まれているのでコメントアウト）
+# GitHub Pages gem
 gem "github-pages", group: :jekyll_plugins
 
-# Jekyll plugins（GitHub Pagesに含まれているもの以外）
-group :jekyll_plugins do
-  gem "jekyll-feed", "~> 0.12"
-  gem "jekyll-sitemap"
-  gem "jekyll-seo-tag"
-  gem "jekyll-remote-theme"
-end
-
-# Windows and JRuby does not include zoneinfo files, so bundle the tzinfo-data gem
-# and associated library.
+# Windows and JRuby support
 platforms :mingw, :x64_mingw, :mswin, :jruby do
   gem "tzinfo", ">= 1", "< 3"
   gem "tzinfo-data"
 end
 
 # Performance-booster for watching directories on Windows
-gem "wdm", "~> 0.1.1", :platforms => [:mingw, :x64_mingw, :mswin]
-
-# Lock `http_parser.rb` gem to `v0.6.x` on JRuby builds since newer versions of the gem
-# do not have a Java counterpart.
-gem "http_parser.rb", "~> 0.6.0", :platforms => [:jruby]
+gem "wdm", "~> 0.1.1", :platforms => [:mingw, :x64_mingw, :mswin]