docs: add tree-sitter integration documentation

[cxxxr]

Add comprehensive documentation for Lem's tree-sitter integration in English and Japanese.

Changes

Tree-sitter Documentation (content/*/development/tree-sitter.md)

• Add documentation in English and Japanese

Contents Covered

• Overview: Features provided by tree-sitter integration (syntax highlighting, indentation, incremental parsing, graceful fallback)
• Architecture: Component diagram showing tree-sitter-cl, lem-tree-sitter, and language modes
• Supported Languages: JSON, YAML, Nix, Markdown, WAT with feature matrix
• Adding Tree-sitter Support: Step-by-step guide for mode developers
  • Creating query files
  • Writing highlight queries with examples
  • Enabling tree-sitter in mode definitions
  • Fallback handling
• Capture Names Reference: Complete mapping of tree-sitter captures to Lem attributes
• Indent Queries: Helix-style @indent/@outdent syntax documentation
• API Reference: enable-tree-sitter-for-mode, tree-sitter-available-p, treesitter-parser class
• Incremental Parsing: How edit tracking and AST reuse works
• Installing Grammars: Instructions for tree-sitter CLI and package managers
• Troubleshooting: Common issues and solutions

Related

• Lem tree-sitter extension: extensions/tree-sitter/
• tree-sitter-cl: https://github.com/lem-project/tree-sitter-cl