actop 1.4.1

Added

• --palette {thermal,viridis,mono} CLI flag and matching DashboardConfig.palette
  field: selects the chart gradient for the session. thermal (default) is the
  existing blue→red gradient, unchanged; viridis is a colorblind-safe perceptual
  ramp; mono is grayscale intensity. Applies at the truecolor and 256-color tiers
  (the 16-color severity ramp and NO_COLOR/none are palette-independent).
  Accessibility-first: a set-once startup preference, not a decorative toggle.

Changed

• --help now surfaces every option's default value (via
  ArgumentDefaultsHelpFormatter), so the supported value set (from choices) and
  the default are documented for all arguments.

Notes

• A runtime color-cycle keybind (peer parity with mactop/macmon's decorative theme
  cycling) was evaluated and deliberately deferred: the startup --palette flag
  delivers the accessibility value, and set-once is the right model for it. See
  docs/DESIGN-system.md §5.2. The palette registry is ordered so the keybind
  remains a purely additive follow-on if ever wanted.