thermald and redbear-upower read_dir /scheme/acpi/{thermal,power} to
enumerate ACPI _TZ zones and _PR power sources. The acpid scheme
returned EIO for these new directory variants, which std::fs::read_dir
interprets as 'the path is not a directory or doesn't exist' and
emits a warning.
Return Ok with no entries for Thermal/Power getdents so read_dir
sees an existing-but-empty directory and consumers gracefully fall
through to the empty-state path.
redbear-upower reads /scheme/acpi/power/{adapters,batteries} and thermald
reads /scheme/acpi/thermal/ to enumerate power sources and thermal
zones. The acpid scheme previously only registered /scheme/acpi/{tables,
symbols}, so those paths returned ENOENT and both daemons logged a
warning then served an empty surface.
Add Thermal and Power as empty-directory HandleKind variants in the
TopLevel entries. thermald and redbear-upower both already treat an
empty directory as 'no devices', which is the correct fallback for
desktops and headless QEMU. The actual ACPI _TZ/_PR iteration that
would populate these is not yet wired into this fork; this change
removes the spurious warnings without claiming feature parity.