Update test coverage drop limit to 0.1%

Author: bact

AGENTS.md

@@ -24,9 +24,11 @@
 - [ ] Complete type annotations for function, method, class, variable, etc.
       Maintain near-100% type annotation coverage.
 - [ ] Add tests for new functionality or behavior.
-      New PR must not drop the test coverage more than 0.2%.
+      New PR must not drop the test coverage more than 0.1%.
 - [ ] Keep the test coverage high. Aim at least 70% test coverage.
 - [ ] Add test cases to cover all code branches and capture edge cases.
+- [ ] `# type: ignore[arg-type]` comment can be used in the test code,
+      only if that specific code want to explicitly test TypeError handling.
 - [ ] Docstring and doctest must reflect the latest code.
 - [ ] All error messages and warning messages should be clear, concise,
       and consistent in style. They should be parseable.