Add EditorConfig for consistent coding style

[yurekami]

Summary

Add .editorconfig to ensure consistent coding style across different editors and IDEs.

Configuration includes:

• Encoding: UTF-8 for all files
• Line endings: LF (Unix-style) for all files
• Python/C++/CUDA/Shell: 4-space indentation
• YAML/CMake/JSON: 2-space indentation
• Makefiles: Tab indentation (required)
• Markdown: Preserves trailing whitespace (needed for line breaks)
• All files: Final newline insertion, trailing whitespace trimming

Benefits

• Ensures contributors use consistent settings regardless of their editor
• Reduces unnecessary whitespace changes in diffs
• Supported natively by most modern editors (VS Code, JetBrains IDEs, Vim, etc.)

See https://editorconfig.org for more information.

Test plan

• Validate EditorConfig syntax
• Verify settings work in VS Code
• Verify settings work in other editors

🤖 Generated with Claude Code