test(auth): build the mocked az path with the host's path rules

Fixes the macOS CI failure. The test hardcoded a Windows absolute path, but the
production code calls os.path.isabs() -- on POSIX runners "C:\Program
Files\..." reads as RELATIVE, so the fallback branch ran and argv[0] was "az"
instead of the resolved path.

Construct the path with os.path.join(os.path.abspath(os.sep), ...) so it is
absolute under the host's rules, and assert against that value. The fallback
test's inputs (".\az.CMD", "az.cmd", "./az") are relative under both ntpath
and posixpath, so they were already portable.

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

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: jawwad-ali

tests/test_authentication.py

@@ -542,19 +542,25 @@ def test_resolve_token_azure_cli_resolves_executable(self):
         entry = AuthConfigEntry(
             hosts=("dev.azure.com",), provider="azure-devops", auth="azure-cli",
         )
+        # Build the absolute path with the HOST's rules: the production code
+        # calls os.path.isabs(), so a hardcoded Windows path would read as
+        # RELATIVE on POSIX runners and silently exercise the fallback branch
+        # instead of the one under test.
+        resolved_path = os.path.join(os.path.abspath(os.sep), "opt", "az", "az.CMD")
+        assert os.path.isabs(resolved_path)
         result = MagicMock()
         result.returncode = 0
         result.stdout = '{"accessToken": "tok"}'
         with patch(
             "specify_cli.authentication.azure_devops.shutil.which",
-            return_value=r"C:\Program Files\az\wbin\az.CMD",
+            return_value=resolved_path,
         ), patch(
             "specify_cli.authentication.azure_devops.subprocess.run",
             return_value=result,
         ) as run:
             assert AzureDevOpsAuth().resolve_token(entry) == "tok"
         argv = run.call_args.args[0]
-        assert argv[0] == r"C:\Program Files\az\wbin\az.CMD"
+        assert argv[0] == resolved_path
         assert argv[1:4] == ["account", "get-access-token", "--resource"]
 
     @pytest.mark.parametrize("which_result", [None, r".\az.CMD", "az.cmd", "./az"])