refactor(aisidebar): restructure project and implement reasoning mode toggle

- Reorganize project structure and file locations
- Add ReasoningController to manage model selection and reasoning mode
- Update design and requirements for reasoning mode toggle
- Implement model switching between Qwen3-4B-Instruct and Qwen3-4B-Thinking models
- Remove deprecated files and consolidate project layout
- Add new steering and specification documentation
- Clean up and remove unnecessary files and directories
- Prepare for enhanced AI sidebar functionality with more flexible model handling

data/conversations/archive_20251026_074828_f11452f2.json

@@ -0,0 +1,23 @@
+{
+  "id": "archive_20251026_074828_f11452f2",
+  "title": "",
+  "created_at": "2025-10-26T07:42:54.664856+00:00",
+  "updated_at": "2025-10-26T07:43:03.637045+00:00",
+  "messages": [
+    {
+      "role": "assistant",
+      "content": "New conversation started. Previous conversation archived.",
+      "timestamp": "2025-10-26T07:42:54.668757+00:00"
+    },
+    {
+      "role": "user",
+      "content": "Hello",
+      "timestamp": "2025-10-26T07:42:59.073389+00:00"
+    },
+    {
+      "role": "assistant",
+      "content": "Hello! How can I assist you today? 😊",
+      "timestamp": "2025-10-26T07:43:03.637045+00:00"
+    }
+  ]
+}