cleanup: remove Windows native support, enforce WSL requirement

Remove Windows batch scripts and native setup instructions since Claude Code CLI
requires WSL on Windows. Consolidate Docker as primary recommendation across all platforms.

Changes:
- Remove setup.bat, run_gemini.bat, setup-docker-env.bat
- Remove examples/claude_config_windows.json
- Update README to clarify WSL requirement for Windows users
- Promote Docker as recommended setup for all platforms
- Update troubleshooting section for WSL-only support
- Apply code formatting fixes from ruff/black

🤖 Generated with [Claude Code](https://claude.ai/code)

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

examples/claude_config_windows.json

@@ -1,13 +0,0 @@
-{
-  "comment": "Traditional Windows configuration (non-Docker)",
-  "comment2": "Replace YOUR_USERNAME with your actual username",
-  "comment3": "Note the double backslashes in the path",
-  "mcpServers": {
-    "gemini": {
-      "command": "C:\\Users\\YOUR_USERNAME\\gemini-mcp-server\\run_gemini.bat",
-      "env": {
-        "GEMINI_API_KEY": "your-gemini-api-key-here"
-      }
-    }
-  }
-}