feat(ui): ✨ implement AI assistant system with full context awareness and tool execution

src/proxy_app/ai_assistant/__init__.py

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+"""
+AI Assistant System for GUI Windows.
+
+A reusable AI assistant that can be integrated into any GUI tool window.
+Provides full context awareness, tool execution, checkpoints for undo,
+and streaming responses with thinking visibility.
+
+Main Components:
+- AIAssistantCore: Main orchestration class
+- WindowContextAdapter: Abstract base for window integration
+- LLMBridge: Async LLM communication bridge
+- CheckpointManager: Undo/rollback capability
+- Tool system: @assistant_tool decorator and execution
+
+Usage:
+    from proxy_app.ai_assistant import AIAssistantCore, WindowContextAdapter
+
+    class MyWindowAdapter(WindowContextAdapter):
+        # Implement abstract methods
+        ...
+
+    core = AIAssistantCore(
+        window_adapter=my_adapter,
+        schedule_on_gui=lambda fn: window.after(0, fn),
+    )
+"""
+
+from .assistant_logger import AssistantLogger
+from .bridge import LLMBridge, StreamCallbacks
+from .checkpoint import Checkpoint, CheckpointManager
+from .context import (
+    WindowContextAdapter,
+    apply_delta,
+    compute_context_diff,
+    compute_delta,
+)
+from .core import AIAssistantCore, ChatSession, Message
+from .prompts import BASE_ASSISTANT_PROMPT, MODEL_FILTER_SYSTEM_PROMPT
+from .tools import (
+    ToolCall,
+    ToolCallSummary,
+    ToolDefinition,
+    ToolExecutor,
+    ToolResult,
+    assistant_tool,
+)
+
+__all__ = [
+    # Core
+    "AIAssistantCore",
+    "ChatSession",
+    "Message",
+    # Bridge
+    "LLMBridge",
+    "StreamCallbacks",
+    # Checkpoint
+    "CheckpointManager",
+    "Checkpoint",
+    # Context
+    "WindowContextAdapter",
+    "compute_context_diff",
+    "compute_delta",
+    "apply_delta",
+    # Tools
+    "assistant_tool",
+    "ToolDefinition",
+    "ToolResult",
+    "ToolCall",
+    "ToolCallSummary",
+    "ToolExecutor",
+    # Prompts
+    "BASE_ASSISTANT_PROMPT",
+    "MODEL_FILTER_SYSTEM_PROMPT",
+    # Logging
+    "AssistantLogger",
+]

src/proxy_app/ai_assistant/adapters/__init__.py

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+"""
+Window Context Adapters for the AI Assistant.
+
+Each adapter connects a specific GUI window to the AI assistant system.
+"""
+
+from .model_filter import ModelFilterWindowContext
+
+__all__ = [
+    "ModelFilterWindowContext",
+]