fix: 修复流式工具调用解析并更新标签格式

主要变更：
- 将工具调用标签从 {} 改为 <invoke></invoke>，避免与 JSON 括号冲突
- 修复流式请求未解析工具调用的问题，现在返回 OpenAI 格式的 tool_calls
- 从 SSE 响应中正确提取 content 并解析工具调用
- 更新提示词格式以使用新标签
- 更新所有相关测试用例

问题修复：
- 流式请求现在正确返回 OpenAI 格式的 tool_calls
- 标签冲突导致的解析失败问题已解决
- 所有单元测试通过 (20/20)
- API 完全兼容 OpenAI REST API tools 字段行为

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/test_response_parser.py

@@ -46,7 +46,7 @@ class TestResponseParser:
         """Test parsing a response with a single tool call."""
         parser = ResponseParser()
         text = f'''I'll check the weather for you.
-{TOOL_CALL_START_TAG}
+<invoke>
 {{
   "name": "get_weather",
   "arguments": {{
@@ -54,7 +54,7 @@ class TestResponseParser:
     "units": "celsius"
   }}
 }}
-{TOOL_CALL_END_TAG}
+</invoke>
 '''
 
         result = parser.parse(text)
@@ -74,14 +74,14 @@ class TestResponseParser:
     def test_parse_response_with_tool_call_no_content(self):
         """Test parsing a response with only a tool call."""
         parser = ResponseParser()
-        text = f'''{TOOL_CALL_START_TAG}
+        text = f'''<invoke>
 {{
   "name": "shell",
   "arguments": {{
     "command": ["ls", "-l"]
   }}
 }}
-{TOOL_CALL_END_TAG}
+</invoke>
 '''
 
         result = parser.parse(text)
@@ -95,9 +95,9 @@ class TestResponseParser:
         """Test parsing a response with malformed JSON in tool call."""
         parser = ResponseParser()
         text = f'''Here's the result.
-{TOOL_CALL_START_TAG}
+<invoke>
 {{invalid json}}
-{TOOL_CALL_END_TAG}
+</invoke>
 '''
 
         result = parser.parse(text)
@@ -109,13 +109,13 @@ class TestResponseParser:
     def test_parse_response_with_missing_tool_name(self):
         """Test parsing a tool call without a name field."""
         parser = ResponseParser()
-        text = f'''{TOOL_CALL_START_TAG}
+        text = f'''<invoke>
 {{
   "arguments": {{
     "command": "echo hello"
   }}
 }}
-{TOOL_CALL_END_TAG}
+</invoke>
 '''
 
         result = parser.parse(text)
@@ -129,7 +129,7 @@ class TestResponseParser:
         """Test parsing a tool call with complex nested arguments."""
         parser = ResponseParser()
         text = f'''Executing command.
-{TOOL_CALL_START_TAG}
+<invoke>
 {{
   "name": "shell",
   "arguments": {{
@@ -140,7 +140,7 @@ class TestResponseParser:
     }}
   }}
 }}
-{TOOL_CALL_END_TAG}
+</invoke>
 '''
 
         result = parser.parse(text)
@@ -182,7 +182,7 @@ class TestResponseParser:
         chunks = [
             "I'll run that ",
             "command for you.",
-            f'{TOOL_CALL_START_TAG}\n{{"name": "shell", "arguments": {{"command": ["echo", "hello"]}}}}\n{TOOL_CALL_END_TAG}'
+            f'<invoke>\n{{"name": "shell", "arguments": {{"command": ["echo", "hello"]}}}}\n</invoke>'
         ]
 
         result = parser.parse_streaming_chunks(chunks)
@@ -267,8 +267,8 @@ class TestResponseParser:
         """Test that tool call IDs are unique."""
         parser = ResponseParser()
 
-        text1 = f'{TOOL_CALL_START_TAG}{{"name": "tool1", "arguments": {{}}}}{TOOL_CALL_END_TAG}'
-        text2 = f'{TOOL_CALL_START_TAG}{{"name": "tool2", "arguments": {{}}}}{TOOL_CALL_END_TAG}'
+        text1 = f'<invoke>{{"name": "tool1", "arguments": {{}}}}</invoke>'
+        text2 = f'<invoke>{{"name": "tool2", "arguments": {{}}}}</invoke>'
 
         result1 = parser.parse(text1)
         result2 = parser.parse(text2)
@@ -286,7 +286,7 @@ class TestConvenienceFunctions:
 
     def test_parse_response_default_parser(self):
         """Test the parse_response convenience function."""
-        text = f'{TOOL_CALL_START_TAG}{{"name": "search", "arguments": {{"query": "test"}}}}{TOOL_CALL_END_TAG}'
+        text = f'<invoke>{{"name": "search", "arguments": {{"query": "test"}}}}</invoke>'
         result = parse_response(text)
 
         assert result.tool_calls is not None
@@ -332,14 +332,14 @@ class TestEdgeCases:
         parser = ResponseParser()
         special_chars = '@#$%^&*()'
         text = f'''Here's the result with special chars: {special_chars}
-{TOOL_CALL_START_TAG}
+<invoke>
 {{
   "name": "test",
   "arguments": {{
     "special": "!@#$%"
   }}
 }}
-{TOOL_CALL_END_TAG}
+</invoke>
 '''
 
         result = parser.parse(text)
@@ -349,7 +349,7 @@ class TestEdgeCases:
     def test_response_with_escaped_quotes(self):
         """Test parsing tool calls with escaped quotes in arguments."""
         parser = ResponseParser()
-        text = f'{TOOL_CALL_START_TAG}{{"name": "echo", "arguments": {{"message": "Hello \\"world\\""}}}}{TOOL_CALL_END_TAG}'
+        text = f'<invoke>{{"name": "echo", "arguments": {{"message": "Hello \\"world\\""}}}}</invoke>'
 
         result = parser.parse(text)
         arguments = json.loads(result.tool_calls[0].function.arguments)
@@ -359,13 +359,13 @@ class TestEdgeCases:
         """Test that only the first tool call is extracted."""
         parser = ResponseParser()
         text = f'''First call.
-{TOOL_CALL_START_TAG}
+<invoke>
 {{"name": "tool1", "arguments": {{}}}}
-{TOOL_CALL_END_TAG}
+</invoke>
 Some text in between.
-{TOOL_CALL_START_TAG}
+<invoke>
 {{"name": "tool2", "arguments": {{}}}}
-{TOOL_CALL_END_TAG}
+</invoke>
 '''
 
         result = parser.parse(text)