Add ErgoScript LSP with real SigmaParser integration (Closes #1097)

[sameezy667]

Closes #1097

Overview

Adds a minimal, production-ready Language Server Protocol (LSP) for ErgoScript with real parser integration. Automatically uses SigmaParser when available, falls back to regex-based validation otherwise. Provides diagnostics, hover, and document symbols for IDE/AI agent support.

What I added

• lsp/server.js — LSP server (Node.js, stdio) with auto-detection of Scala parser
• lsp/ParserCLI.scala — Scala CLI wrapper that invokes SigmaParser and outputs JSON diagnostics
• lsp/package.json — Node dependencies (vscode-languageserver)
• lsp/README.md — Setup, architecture diagram, usage instructions
• lsp/example.es — Sample ErgoScript file for testing
• lsp/test_parser.sh — Test script for parser CLI

How it works

Real parser mode (recommended):

1. Run sbt "parsers/publishLocal" to build parser JAR
2. LSP auto-detects JAR and spawns scala CLI to invoke ParserCLI.scala
3. Gets accurate parse errors with line/column from SigmaParser

Fallback mode (no build required):

• If JAR not found, uses regex-based validation
• Checks for unmatched braces, TODO markers
• Still provides hover and symbols

Architecture

LSP Client → server.js → ParserCLI.scala → SigmaParser (fastparse)
↘ regex fallback (if no JAR)

How to test

# Build parser
sbt "parsers/publishLocal"

# Run LSP server
cd lsp
npm install
npm start
Then connect any LSP client (VS Code extension, Neovim, etc.) to the stdio server at node lsp/server.js.

Test files manually:
cd lsp
./test_parser.sh