feat: add cpToInstance and cpFromInstance functions

Add manually-maintained cp functionality to the SDK for copying files
to/from running instances. This is placed in src/lib/ directory following
the SDK's convention for custom extensions.

Features:
- cpToInstance: Copy local file/directory to instance
- cpFromInstance: Copy file/directory from instance to local
- WebSocket-based streaming with JSON control messages
- Supports files and recursive directory operations
- Handles symlinks, permissions, and modification times
- Chunked binary data transfer for efficient streaming

Adds ws as a peer dependency for WebSocket support.

Author: rgarcia

package.json

@@ -26,13 +26,16 @@
     "lint": "./scripts/lint",
     "fix": "./scripts/format"
   },
-  "dependencies": {},
+  "dependencies": {
+    "ws": "^8.18.3"
+  },
   "devDependencies": {
     "@arethetypeswrong/cli": "^0.17.0",
     "@swc/core": "^1.3.102",
     "@swc/jest": "^0.2.29",
     "@types/jest": "^29.4.0",
     "@types/node": "^20.17.6",
+    "@types/ws": "^8.18.1",
     "@typescript-eslint/eslint-plugin": "8.31.1",
     "@typescript-eslint/parser": "8.31.1",
     "eslint": "^9.39.1",