test: cover explicit git -C terminal probe

native_mcp_preference.py

@@ -380,11 +380,15 @@ def _resolve_executable(cwd: str | None, executable: str | None) -> str | None:
     if not executable:
         return None
     if os.path.isabs(executable):
-        return executable if os.path.exists(executable) and os.access(executable, os.X_OK) else None
+        if os.path.exists(executable) and os.access(executable, os.X_OK):
+            return executable
+        return None
     if "/" in executable or "\\" in executable:
         target_cwd = cwd or os.getcwd()
         full_path = os.path.abspath(os.path.join(target_cwd, executable))
-        return full_path if os.path.exists(full_path) and os.access(full_path, os.X_OK) else None
+        if os.path.exists(full_path) and os.access(full_path, os.X_OK):
+            return full_path
+        return None
     return shutil.which(executable)
 
 
@@ -443,7 +447,10 @@ def diagnose_terminal_failure(cwd: str | None, command: list[str]) -> dict[str,
     if not has_any_shell:
         diagnostics["shell_exists"] = False
         diagnostics["error_type"] = "missing shell"
-        diagnostics["error_msg"] = "No standard system shell (/bin/sh, /bin/zsh, /bin/bash) is available or executable."
+        diagnostics["error_msg"] = (
+            "No standard system shell (/bin/sh, /bin/zsh, /bin/bash) is "
+            "available or executable."
+        )
         return diagnostics
 
     return diagnostics