feat: improve editor tooling and fix warnings

Neovim improvements:
- Add tree-sitter text objects for functions, types, blocks
- Add folding support
- Enhanced REPL integration (toggle, send line/selection)
- New commands: LuxCheck, LuxReplToggle, LuxSend
- Better keybindings with localleader

VS Code extension:
- Full syntax highlighting with TextMate grammar
- LSP client integration
- 20+ snippets for common patterns
- Commands: run, format, check, REPL
- Keybindings and context menu

Fixes:
- Fix all cargo warnings with #[allow(dead_code)] annotations
- Clean up unused variables

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

editors/vscode/package.json

@@ -0,0 +1,150 @@
+{
+  "name": "lux-lang",
+  "displayName": "Lux Language",
+  "description": "Language support for Lux - a functional language with algebraic effects",
+  "version": "0.1.0",
+  "publisher": "lux-lang",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/lux-lang/lux"
+  },
+  "engines": {
+    "vscode": "^1.75.0"
+  },
+  "categories": [
+    "Programming Languages"
+  ],
+  "keywords": [
+    "lux",
+    "functional",
+    "effects",
+    "algebraic effects"
+  ],
+  "activationEvents": [
+    "onLanguage:lux"
+  ],
+  "main": "./out/extension.js",
+  "contributes": {
+    "languages": [
+      {
+        "id": "lux",
+        "aliases": ["Lux", "lux"],
+        "extensions": [".lux"],
+        "configuration": "./language-configuration.json",
+        "icon": {
+          "light": "./icons/lux-light.png",
+          "dark": "./icons/lux-dark.png"
+        }
+      }
+    ],
+    "grammars": [
+      {
+        "language": "lux",
+        "scopeName": "source.lux",
+        "path": "./syntaxes/lux.tmLanguage.json"
+      }
+    ],
+    "configuration": {
+      "title": "Lux",
+      "properties": {
+        "lux.lspPath": {
+          "type": "string",
+          "default": "",
+          "description": "Path to the Lux binary. If empty, searches PATH."
+        },
+        "lux.lsp.enabled": {
+          "type": "boolean",
+          "default": true,
+          "description": "Enable the Lux language server"
+        },
+        "lux.format.onSave": {
+          "type": "boolean",
+          "default": false,
+          "description": "Format files on save"
+        },
+        "lux.diagnostics.enabled": {
+          "type": "boolean",
+          "default": true,
+          "description": "Enable inline diagnostics"
+        }
+      }
+    },
+    "commands": [
+      {
+        "command": "lux.run",
+        "title": "Lux: Run Current File"
+      },
+      {
+        "command": "lux.format",
+        "title": "Lux: Format Document"
+      },
+      {
+        "command": "lux.check",
+        "title": "Lux: Type Check File"
+      },
+      {
+        "command": "lux.startRepl",
+        "title": "Lux: Start REPL"
+      },
+      {
+        "command": "lux.sendToRepl",
+        "title": "Lux: Send Selection to REPL"
+      },
+      {
+        "command": "lux.restartLsp",
+        "title": "Lux: Restart Language Server"
+      }
+    ],
+    "keybindings": [
+      {
+        "command": "lux.run",
+        "key": "ctrl+shift+r",
+        "mac": "cmd+shift+r",
+        "when": "editorLangId == lux"
+      },
+      {
+        "command": "lux.sendToRepl",
+        "key": "ctrl+enter",
+        "mac": "cmd+enter",
+        "when": "editorLangId == lux && editorHasSelection"
+      }
+    ],
+    "menus": {
+      "editor/context": [
+        {
+          "command": "lux.run",
+          "when": "editorLangId == lux",
+          "group": "lux"
+        },
+        {
+          "command": "lux.sendToRepl",
+          "when": "editorLangId == lux && editorHasSelection",
+          "group": "lux"
+        }
+      ]
+    },
+    "snippets": [
+      {
+        "language": "lux",
+        "path": "./snippets/lux.json"
+      }
+    ]
+  },
+  "scripts": {
+    "vscode:prepublish": "npm run compile",
+    "compile": "tsc -p ./",
+    "watch": "tsc -watch -p ./",
+    "lint": "eslint src --ext ts"
+  },
+  "devDependencies": {
+    "@types/node": "^18.x",
+    "@types/vscode": "^1.75.0",
+    "@typescript-eslint/eslint-plugin": "^6.0.0",
+    "@typescript-eslint/parser": "^6.0.0",
+    "eslint": "^8.0.0",
+    "typescript": "^5.0.0"
+  },
+  "dependencies": {
+    "vscode-languageclient": "^9.0.0"
+  }
+}