feat(aisidebar): implement Ollama availability handling and graceful startup

- Add comprehensive Ollama connection error handling strategy
- Implement OllamaClient with non-blocking initialization and connection checks
- Create OllamaAvailabilityMonitor for periodic Ollama connection tracking
- Update design and requirements to support graceful Ollama unavailability
- Add new project structure for AI sidebar module with initial implementation
- Enhance error handling to prevent application crashes when Ollama is not running
- Prepare for future improvements in AI sidebar interaction and resilience

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

@@ -329,6 +329,31 @@ class PreferencesState:
 
 ## Error Handling
 
+### Ollama Unavailability
+
+- **Startup Without Ollama**: Initialize all components successfully, show status message in UI
+- **Model List Failure**: Return empty list, display "Ollama not running" in model label
+- **Chat Request Without Ollama**: Display friendly message: "Please start Ollama to use AI features"
+- **Connection Lost Mid-Stream**: Display partial response + reconnection instructions
+- **Periodic Availability Check**: Attempt to reconnect every 30s when unavailable (non-blocking)
+
+#### Implementation Strategy
+
+```python
+class OllamaClient:
+    def __init__(self, host: str | None = None) -> None:
+        # Never raise exceptions during initialization
+        # Set _available = False if connection fails
+        
+    def list_models(self) -> list[str]:
+        # Return empty list instead of raising on connection failure
+        # Log warning but don't crash
+        
+    def chat(self, ...) -> dict[str, str] | None:
+        # Return error message dict instead of raising
+        # {"role": "assistant", "content": "Ollama unavailable..."}
+```
+
 ### Streaming Errors
 
 - **Connection Lost**: Display partial response + error message, allow retry
@@ -422,6 +447,32 @@ class PreferencesState:
 - Preferences file is optional; defaults work without it
 - Graceful degradation if gtk4-layer-shell unavailable
 
+### Ollama Availability Detection
+
+Add periodic checking mechanism to detect when Ollama becomes available:
+
+```python
+class OllamaAvailabilityMonitor:
+    """Monitors Ollama availability and notifies UI of state changes."""
+    
+    def __init__(self, client: OllamaClient, callback: Callable[[bool], None]):
+        self._client = client
+        self._callback = callback
+        self._last_state = False
+        self._check_interval = 30  # seconds
+        
+    def start_monitoring(self) -> None:
+        """Begin periodic availability checks via GLib.timeout_add."""
+        
+    def _check_availability(self) -> bool:
+        """Check if Ollama is available and notify on state change."""
+```
+
+Integration in SidebarWindow:
+- Initialize monitor on startup
+- Update UI state when availability changes (enable/disable input, update status message)
+- Show notification when Ollama becomes available: "Ollama connected - AI features enabled"
+
 ### Future Enhancements
 
 - Command history with up/down arrow navigation

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

@@ -71,3 +71,15 @@ This document outlines the requirements for enhancing the AI sidebar module for
 3. WHEN reasoning mode is disabled, THE AI Sidebar SHALL request and display only the final answer without intermediate reasoning
 4. THE AI Sidebar SHALL persist the reasoning mode preference across conversation sessions
 5. THE AI Sidebar SHALL visually distinguish reasoning content from final answer content when reasoning mode is enabled
+
+### Requirement 6: Graceful Ollama Unavailability Handling
+
+**User Story:** As a user, I want the AI Sidebar to start and function even when Ollama is not running, so that Ignis can launch successfully and I can start Ollama when I'm ready to use the AI features.
+
+#### Acceptance Criteria
+
+1. WHEN Ollama is not running at startup, THE AI Sidebar SHALL initialize successfully without blocking Ignis startup
+2. WHEN Ollama is unavailable, THE AI Sidebar SHALL display a clear message instructing the user to start Ollama
+3. WHEN the user attempts to send a message while Ollama is unavailable, THE AI Sidebar SHALL display a helpful error message instead of crashing
+4. WHEN Ollama becomes available after startup, THE AI Sidebar SHALL detect the availability and enable chat functionality without requiring a restart
+5. THE AI Sidebar SHALL handle Ollama connection failures gracefully during model listing, switching, and chat operations

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

@@ -97,7 +97,37 @@
   - Update message rendering to handle reasoning metadata
   - _Requirements: 5.5_
 
-- [ ] 8. Add error handling and edge cases
+- [-] 8. Implement graceful Ollama unavailability handling
+- [ ] 8.1 Update OllamaClient initialization
+  - Modify `__init__()` to never raise exceptions during initialization
+  - Add connection check that sets internal availability flag
+  - Update `list_models()` to return empty list instead of raising on connection failure
+  - Update `chat()` and `stream_chat()` to return error messages instead of raising
+  - _Requirements: 6.1, 6.3, 6.5_
+
+- [ ] 8.2 Create OllamaAvailabilityMonitor
+  - Create `ollama_monitor.py` with OllamaAvailabilityMonitor class
+  - Implement periodic availability checking using GLib.timeout_add (30s interval)
+  - Add callback mechanism to notify UI of state changes
+  - Ensure checks are non-blocking and don't impact UI responsiveness
+  - _Requirements: 6.4_
+
+- [ ] 8.3 Update SidebarWindow for Ollama unavailability
+  - Initialize OllamaAvailabilityMonitor in SidebarWindow
+  - Display "Ollama not running" status message when unavailable at startup
+  - Update model label to show connection status
+  - Disable input field when Ollama unavailable, show helpful message
+  - Add callback to re-enable features when Ollama becomes available
+  - _Requirements: 6.1, 6.2, 6.4_
+
+- [ ] 8.4 Add user-friendly error messages
+  - Display clear instructions when user tries to chat without Ollama
+  - Show notification when Ollama connection is restored
+  - Update all command handlers to check Ollama availability
+  - Provide actionable error messages (e.g., "Start Ollama with: ollama serve")
+  - _Requirements: 6.2, 6.3_
+
+- [ ] 9. Add error handling and edge cases
   - Implement stream timeout handling (60s limit) with cancellation
   - Add connection error recovery for streaming failures
   - Handle command execution during active streaming
@@ -105,10 +135,11 @@
   - Implement graceful degradation for missing preferences file
   - _Requirements: 1.4, 3.5, 4.3, 4.4_
 
-- [ ] 9. Polish and integration
+- [ ] 10. Polish and integration
   - Add CSS styling for system messages, reasoning content, and streaming indicator
   - Implement `/help` command to display available commands
   - Add visual feedback for command execution (loading states)
   - Ensure all UI updates maintain smooth scrolling behavior
   - Test keyboard focus management across all new widgets
-  - _Requirements: 1.3, 2.3, 3.5, 5.5_
+  - Add status indicator in UI showing Ollama connection state
+  - _Requirements: 1.3, 2.3, 3.5, 5.5, 6.2_