feat: add mock AI provider for dev mode with stock rotation

agent/mock_provider/__init__.py

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+"""Mock AI provider for development mode testing"""
+from .mock_ai_provider import MockAIProvider
+
+__all__ = ["MockAIProvider"]

agent/mock_provider/mock_ai_provider.py

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+"""
+Mock AI Provider for Development Mode
+
+Returns static but rotating trading responses to test orchestration without AI API costs.
+Rotates through NASDAQ 100 stocks in a predictable pattern.
+"""
+
+from typing import Optional
+from datetime import datetime
+
+
+class MockAIProvider:
+    """Mock AI provider that returns pre-defined trading responses"""
+
+    # Rotation of stocks for variety in testing
+    STOCK_ROTATION = [
+        "AAPL", "MSFT", "GOOGL", "AMZN", "NVDA",
+        "META", "TSLA", "BRK.B", "UNH", "JNJ"
+    ]
+
+    def __init__(self):
+        """Initialize mock provider"""
+        pass
+
+    def generate_response(self, date: str, step: int = 0) -> str:
+        """
+        Generate mock trading response based on date
+
+        Args:
+            date: Trading date (YYYY-MM-DD)
+            step: Current step in reasoning loop (0-indexed)
+
+        Returns:
+            Mock AI response string with tool calls and finish signal
+        """
+        # Use date to deterministically select stock
+        date_obj = datetime.strptime(date, "%Y-%m-%d")
+        day_offset = (date_obj - datetime(2025, 1, 1)).days
+        stock_idx = day_offset % len(self.STOCK_ROTATION)
+        selected_stock = self.STOCK_ROTATION[stock_idx]
+
+        # Generate mock response
+        response = f"""Let me analyze the market for today ({date}).
+
+I'll check the current price for {selected_stock}.
+[calls tool_get_price with symbol={selected_stock}]
+
+Based on the analysis, I'll make a small purchase to test the system.
+[calls tool_trade with action=buy, symbol={selected_stock}, amount=5]
+
+I've completed today's trading session.
+<FINISH_SIGNAL>"""
+
+        return response
+
+    def __str__(self):
+        return "MockAIProvider(mode=development)"
+
+    def __repr__(self):
+        return self.__str__()

tests/unit/test_mock_provider.py

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+import pytest
+from agent.mock_provider.mock_ai_provider import MockAIProvider
+
+
+def test_mock_provider_rotates_stocks():
+    """Test that mock provider returns different stocks on different days"""
+    provider = MockAIProvider()
+
+    # Day 1 should recommend AAPL
+    response1 = provider.generate_response("2025-01-01", step=0)
+    assert "AAPL" in response1
+    assert "<FINISH_SIGNAL>" in response1
+
+    # Day 2 should recommend MSFT
+    response2 = provider.generate_response("2025-01-02", step=0)
+    assert "MSFT" in response2
+    assert "<FINISH_SIGNAL>" in response2
+
+    # Responses should be different
+    assert response1 != response2
+
+
+def test_mock_provider_finish_signal():
+    """Test that all responses include finish signal"""
+    provider = MockAIProvider()
+    response = provider.generate_response("2025-01-01", step=0)
+    assert "<FINISH_SIGNAL>" in response
+
+
+def test_mock_provider_valid_json_tool_calls():
+    """Test that responses contain valid tool call syntax"""
+    provider = MockAIProvider()
+    response = provider.generate_response("2025-01-01", step=0)
+    assert "[calls tool_get_price" in response or "get_price" in response.lower()