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

tests/unit/test_mock_provider.py

@@ -0,0 +1,34 @@
+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()