feat: replace edit mode with plan agent and overall exercise updates

Author: FidelusAleksander

.devcontainer/devcontainer.json

@@ -1,6 +1,6 @@
 {
   "name": "Python 3",
-  "image": "mcr.microsoft.com/devcontainers/python:3.13",
+  "image": "mcr.microsoft.com/vscode/devcontainers/python:3.13",
   "forwardPorts": [8000],
   "postCreateCommand": "pip install -r requirements.txt",
   "customizations": {