chore: 添加 .codeccignore 排除测试 fixture 的误报

CodeCC 将测试样本中的假凭据误报为敏感信息泄露，
这些文件是 ReviewMind 的测试用例，用于验证敏感信息检测功能。

Author: Stelquis

.codeccignore

@@ -0,0 +1,10 @@
+# CodeCC ignore rules
+#
+# These files are intentionally excluded from CodeCC secret scanning
+# because they are test fixtures containing fake/dummy credentials
+# used to validate the ReviewMind secret detection functionality.
+
+# ReviewMind test fixtures with fake secrets (for testing secret detection)
+examples/skills_code_review_agent/evals/fixtures/*.diff
+examples/skills_code_review_agent/evals/hidden_fixtures/*.diff
+examples/skills_code_review_agent/evals/hidden_samples.py