test: enhance test framework with comprehensive fixtures and mocks (#5354)

* test: enhance test framework with comprehensive fixtures and mocks

- Add shared mock builders for aiocqhttp, discord, telegram
- Add test helpers for platform configs and mock objects
- Expand conftest.py with test profile support
- Update coverage test workflow configuration

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* refactor(tests): 移动并重构模拟 LLM 响应和消息组件函数

* fix(tests): 优化 pytest_runtest_setup 中的标记检查逻辑

---------

Co-authored-by: whatevertogo <whatevertogo@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/fixtures/plugins/fixture_plugin.py

@@ -0,0 +1,40 @@
+"""
+测试插件 - 用于插件系统测试
+
+这是一个最小化的测试插件，用于验证插件系统的功能。
+"""
+
+from astrbot.api import llm_tool, star
+from astrbot.api.event import AstrMessageEvent, MessageEventResult, filter
+
+
+@star.register("test_plugin", "AstrBot Team", "测试插件 - 用于插件系统测试", "1.0.0")
+class TestPlugin(star.Star):
+    """测试插件类"""
+
+    def __init__(self, context: star.Context) -> None:
+        super().__init__(context)
+        self.initialized = True
+
+    async def terminate(self) -> None:
+        """插件终止"""
+        self.initialized = False
+
+    @filter.command("test_cmd")
+    async def test_command(self, event: AstrMessageEvent) -> None:
+        """测试命令处理器。"""
+        event.set_result(MessageEventResult().message("测试命令执行成功"))
+
+    @llm_tool("test_tool")
+    async def test_llm_tool(self, query: str) -> str:
+        """测试 LLM 工具。
+
+        Args:
+            query(string): 查询内容。
+        """
+        return f"测试工具执行成功: {query}"
+
+    @filter.regex(r"^test_regex_(.+)$")
+    async def test_regex_handler(self, event: AstrMessageEvent) -> None:
+        """测试正则处理器。"""
+        event.set_result(MessageEventResult().message("正则匹配成功"))