feat(ci): add power_only toggle and extended physical power audit

- New `power_only` workflow_dispatch boolean input (default: false)
- When power_only=true: virtual-ux matrix is skipped entirely
- virtual-power extends to 20 min (was 15 min); job timeout bumped to 40 min
- Physical job: forces 20 min Robo, ignores timeout input, full power report
- Enhanced physical summariser (power_only mode): full wakelock list grouped
  by package, all alarms with per-package frequency, CPU wakeups, screen-on
  time, background CPU, app AlarmManager calls, Doze/DeviceIdle events
- Physical job timeout-minutes bumped to 45 to cover 20 min test + overhead

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Rob