Feature/issue 117 lsp vscode extension

[yaswanth169]

Summary

• Adds a Java LSP server (edu.cmu.cs.sasylf.lsp) built on LSP4J 0.21.1,
  reusing 100% of the existing SASyLF parser and typechecker
• Adds a VSCode extension (vscode-sasylf/) with syntax highlighting,
  real-time diagnostics, hover, code completion, document symbols,
  and go-to-definition
• Packages as a fat JAR (sasylf-lsp.jar) and .vsix for easy install

Features

• Diagnostics: Real-time error/warning squiggles from the SASyLF typechecker
• Syntax Highlighting: TextMate grammar for keywords, rule separators,
  comments, ::=
• Document Symbols: Outline view showing syntax, judgments (with nested
  rules), and theorems
• Hover: Shows judgment form, theorem kind, syntax info on mouse-over
• Completion: Keywords + all in-scope theorems, rules, judgments, syntax
• Go to Definition: Jump to declaration in the current file

How to install

cd vscode-sasylf
npm install && npx tsc -p ./
npx @vscode/vsce package --allow-missing-repository
code --install-extension sasylf-0.1.0.vsix

Test plan

• Open a .slf file in VSCode — syntax highlighting appears
• Errors/warnings show as squiggles in real time
• Outline view shows judgments, theorems, syntax
• Hover on a judgment/theorem shows its info
• Completion suggests keywords and rule/theorem names
• Existing regression tests still pass (182/188, same as master)

Fixes #117.

[boyland]

This is an unacceptable PR. It includes far too many things. It also seems ignorant of the fact that there already is a PR about the lsp. Don't do another PR yet on the existing PR.

[yaswanth169]

Regarding the LSP work, I had already gone through the existing PR earlier while working on this, and I was aware of its direction. While reviewing it, I noticed a few areas where some edge cases or completeness might need further attention, especially around integration with the current parser/typechecker and certain feature behaviors.

Over the past couple of months, I’ve been working closely with the codebase and diving fairly deep into it, so this implementation was an attempt to explore those gaps and extend the functionality further.

That said, I understand your concern about the size and scope of this PR it does bundle too many things together. I’ll pause on this and instead align with the existing PR, contributing in a more focused and incremental way.

I’ll also check with you before proceeding further to make sure everything stays aligned with the project direction.