Fix CI: use ruby platform for cross-platform compatibility

Use ruby platform for gems to compile from source on CI runners,
avoiding platform-specific gem conflicts.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: andreibondarev

Gemfile.lock

@@ -118,8 +118,6 @@ GEM
     erubi (1.13.1)
     ffi (1.17.3)
     ffi (1.17.3-arm64-darwin)
-    ffi (1.17.3-x86_64-darwin)
-    ffi (1.17.3-x86_64-linux-gnu)
     globalid (1.3.0)
       activesupport (>= 6.1)
     i18n (1.14.8)
@@ -179,10 +177,6 @@ GEM
       racc (~> 1.4)
     nokogiri (1.18.10-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.18.10-x86_64-darwin)
-      racc (~> 1.4)
-    nokogiri (1.18.10-x86_64-linux-gnu)
-      racc (~> 1.4)
     parallel (1.27.0)
     parser (3.3.10.1)
       ast (~> 2.4.1)
@@ -307,8 +301,6 @@ GEM
     sqlite3 (2.8.1)
       mini_portile2 (~> 2.8.0)
     sqlite3 (2.8.1-arm64-darwin)
-    sqlite3 (2.8.1-x86_64-darwin)
-    sqlite3 (2.8.1-x86_64-linux-gnu)
     standard (1.53.0)
       language_server-protocol (~> 3.17.0.2)
       lint_roller (~> 1.0)
@@ -341,8 +333,6 @@ GEM
 PLATFORMS
   arm64-darwin
   ruby
-  x86_64-darwin
-  x86_64-linux-gnu
 
 DEPENDENCIES
   administrate (~> 0.19.0)