Update .gitignore to prevent AI-generated markdown files

Block all .md files by default except:
- Whitelisted documentation files (README, LICENSE, etc.)
- Files within .docc documentation catalogs

Author: coenttb

.gitignore

@@ -1,40 +1,25 @@
-# Swift
-.build/
-.swiftpm/
-Package.resolved
-
-# Environment files
-.env*
-
-# Xcode
-*.xcodeproj
-*.xcworkspace
-*.xcuserdata
-DerivedData/
-
-# IDEs
-.vscode/
-.idea/
-*.swp
-*.swo
 *~
 
-# Generated by MacOS
-.DS_Store
-
-# Generated by Windows
+Package.resolved
+DerivedData/
 Thumbs.db
 
-# Generated by Linux
-*~
-
-# Log files
-*.log
-
-# AI
-.claude
-CLAUDE.MD
-
-# Temporary files
-*.tmp
-*.temp
+# Dot files/directories (opt-in only)
+/.*
+!/.github
+!/.gitignore
+!/.spi.yml
+!/.swift-format
+!/.swiftformat
+!/.swiftlint.yml
+
+# Documentation (opt-in for whitelisted .md files and .docc catalogs only)
+# Blocks all .md files by default to prevent AI-generated content from being committed
+*.md
+!README.md
+!LICENSE.md
+!CHANGELOG.md
+!CONTRIBUTING.md
+!CODE_OF_CONDUCT.md
+!SECURITY.md
+!**/*.docc/**/*.md