Adds battery-state awareness to the thread-count helper: when
probe_power_state() returns OnBattery, chosen is halved before the
[MIN, MAX] clamp. Also removes the leading underscore from the
workload/gpu_offloaded parameters (they are silenced via let _ = ...
until the GPU-clamp task).
New test battery_halves_thread_count verifies on_battery <= on_ac and
>= MIN when the host has more than MIN physical cores. Restructured
to sequential with_override calls (not nested) to avoid re-entrant
deadlock on power::TEST_LOCK.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
847dc755ac