Integrate lua-language-server (LuaLS) with Monaco editor in Electron app

[Copilot]

Wires LuaLS into the Monaco editor so Grid firmware scripts get proper LSP-backed completions, hover docs, and diagnostics — including the full Grid API surface — without adding heavy client-side LSP framework dependencies.

Architecture

Renderer (Monaco)
    │  native WebSocket  ws://127.0.0.1:<dynamic-port>
    ▼
WebSocket proxy  (Electron main)
    │  JSON-RPC over stdio  (LSP wire format)
    ▼
lua-language-server binary

• No new npm dependencies — proxy uses the existing ws package; renderer uses native WebSocket.
• Graceful degradation — port 0 disables all LSP features silently (web build, CI without binary download).
• LuaLS always receives languageId: "lua" regardless of whether the Monaco model is intech_lua or lua.

New files

• build-scripts/download-lua-ls.js — downloads the platform-appropriate LuaLS binary from GitHub Releases into resources/lua-language-server/. Called automatically before every export:* script.
• src/electron/src/lua-language-server.ts — spawns LuaLS with --stdio, frames/deframes LSP Content-Length headers, proxies each WS client to its own LuaLS process in an isolated temp workspace.
• src/renderer/lib/lua-ls-client.ts — lightweight LSP client: initialize handshake, textDocument/did* sync, Monaco provider registration for completions, hover, and diagnostics.
• src/renderer/assets/lua/annotations/grid.lua — EmmyLua annotation file covering the full Grid API: GridElement class with all element-type methods, all global functions (midi_send, page_load, led_color, …), and self/element[] pre-declarations.

Modified files

• src/electron/main.ts — starts LuaLS proxy on app.whenReady, stops on before-quit, exposes port via synchronous IPC.
• src/electron/preload.ts — surfaces window.electron.luaLanguageServer.getPort().
• src/renderer/lib/monaco.ts — calls initLuaLsClient(port) at module init.
• electron-builder-config.js — bundles resources/lua-language-server/ as extraResources.
• package.json — adds download-lua-ls script; prepends it to all export:* pipelines.

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