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

.kiro/specs/ai-sidebar-enhancements/design.md

@@ -233,7 +233,11 @@ class ConversationArchive:
 
 ```python
 class ReasoningController:
-    """Manages reasoning mode state and API parameters."""
+    """Manages reasoning mode state and model selection."""
+    
+    # Model names for reasoning toggle
+    INSTRUCT_MODEL = "hf.co/unsloth/Qwen3-4B-Instruct-2507-GGUF:Q8_K_XL"
+    THINKING_MODEL = "hf.co/unsloth/Qwen3-4B-Thinking-2507-GGUF:Q8_K_XL"
     
     def __init__(self):
         self._enabled = False
@@ -245,8 +249,9 @@ class ReasoningController:
     def toggle(self) -> bool:
         """Toggle reasoning mode and persist preference."""
         
-    def get_chat_options(self) -> dict:
-        """Return Ollama API options for reasoning mode."""
+    def get_model_name(self) -> str:
+        """Return the appropriate model name based on reasoning mode."""
+        return self.THINKING_MODEL if self._enabled else self.INSTRUCT_MODEL
 ```
 
 #### UI Components
@@ -254,41 +259,35 @@ class ReasoningController:
 Add toggle button to header area:
 
 ```python
-self._reasoning_toggle = Gtk.ToggleButton(label="🧠 Reasoning")
-self._reasoning_toggle.connect("toggled", self._on_reasoning_toggled)
+self._reasoning_toggle = widgets.Button(label="🧠 Reasoning: OFF")
+self._reasoning_toggle.connect("clicked", self._on_reasoning_toggled)
 ```
 
 #### Ollama Integration
 
-When reasoning mode is enabled, pass additional options to Ollama:
+When reasoning mode is toggled, switch between models:
 
 ```python
-# Standard mode
-ollama.chat(model=model, messages=messages)
+# Get model based on reasoning mode
+model = self._reasoning_controller.get_model_name()
 
-# Reasoning mode (model-dependent)
-ollama.chat(
-    model=model,
-    messages=messages,
-    options={
-        "temperature": 0.7,
-        # Model-specific reasoning parameters
-    }
-)
+# Use the selected model for chat
+ollama.chat(model=model, messages=messages)
 ```
 
 #### Message Formatting
 
-When reasoning is enabled and model supports it:
+When using the thinking model:
 - Display thinking process in distinct style (italic, gray text)
 - Separate reasoning from final answer with visual divider
-- Use expandable/collapsible section for reasoning (optional)
+- Parse `<think>` tags from model output to extract reasoning content
 
 #### Persistence
 
 - Save reasoning preference to `~/.config/aisidebar/preferences.json`
 - Load preference on startup
 - Apply to all new conversations
+- Automatically switch models when preference changes
 
 ## Data Models