The previous commit changed the existence probe from is_dir/exists
(read_dir uses stat) to read_dir.is_ok(), but the second and subsequent
calls to read_dir for /scheme/acpi/thermal still return Err at runtime.
The first discover_zone_dirs call at startup succeeds (it sees 0 zones,
matching the acpid scheme's empty Thermal directory). The periodic
monitor_loop recheck then fails with 'unavailable' even though the
path is in fact present.
The real reason is not fully understood yet, but may relate to
scheme-namespace state after userland init, fd table churn, or
Redox-specific read_dir semantics on empty scheme directories.
The warn-once check is redundant: discover_zone_dirs already runs at
startup, and update_policy() sees the empty state every poll cycle and
re-renders the TUI accordingly. Drop the periodic recheck so the
already-diagnosed empty surface no longer logs a false alarm.
vasilito
fd4a40eff3