The 'absolute paths pass through unchanged' test for _load_idedata
hardcoded a POSIX-style absolute path ('/somewhere/else/bootloader.bin').
On Windows, Path.is_absolute() returns False for that shape -- absolute
paths there require a drive letter -- so _resolve_prebuilt_idedata_paths
classified it as relative and prepended CORE.prebuilt_dir, breaking the
test's assertion.
Replace the hardcoded POSIX path with a tmp_path-rooted one so it's
platform-absolute on every runner. No production code change; this is a
test-only fix surfaced by the windows-latest pytest matrix on PR #16348.
Note: the macOS 3.14 failure on the same CI run is a flaky timing test
(tests/dashboard/test_web_server.py::test_dashboard_subscriber_entries_update_interval,
50ms sleep expecting 2+ iterations at 10ms) unrelated to this PR.
Issue: esphome/device-builder#572