Add new VSCode command to show syntax tree

[Copilot]

This PR adds a new VSCode command Roughly: Show Syntax Tree that displays the Abstract Syntax Tree (AST) of the currently active R file.

Implementation Details

• Command: roughly.showSyntaxTree - opens AST output in a virtual document beside the current editor
• Execution: Uses the existing CLI command roughly debug ast <file> via child process
• Display: Creates a virtual document provider that shows the formatted AST output
• Error Handling: Proper validation for R files, saved files, and command execution failures

Usage

1. Open an R file in VSCode
2. Use Command Palette (Ctrl+Shift+P / Cmd+Shift+P)
3. Type "Roughly: Show Syntax Tree"
4. AST opens in new editor tab beside current file

Example

For R code:

library(dplyr)
data <- data.frame(x = 1:3, y = 4:6)
result <- data %>% filter(x > 1)

The command shows detailed AST structure including:

• Program structure and comments
• Function calls and library imports
• Variable assignments and operators
• Pipeline operations and function arguments
• Data structure definitions

Technical Implementation

• Reuses existing binary resolution logic from server commands
• Follows functional programming style as requested
• Minimal changes with focused functionality
• Proper TypeScript typing and error handling
• Added ESLint configuration for code quality
• Virtual document provider for read-only AST display

Testing

• Manually tested with various R code examples (functions, data manipulation, ggplot2)
• Verified extension compiles without errors
• Tested error scenarios (non-R files, unsaved files, binary failures)
• Confirmed AST output matches CLI roughly debug ast functionality

Fixes #54.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.