* Add set-color/clear-color workspace actions for tab color via CLI
Expose the existing tab color functionality through the workspace-action
CLI command, enabling programmatic tab color setting without the GUI
context menu.
Supports both named colors (Red, Blue, Amber, etc.) and hex values
(#RRGGBB). Named colors resolve against the built-in palette via
case-insensitive matching.
Usage:
cmux workspace-action --action set-color --color blue
cmux workspace-action --action set-color --color "#C0392B"
cmux workspace-action set-color Amber
cmux workspace-action clear-color
* Return explicit null color in clear_color JSON response
Restore "color": null in the clear_color response payload so JSON
consumers can distinguish "color was cleared" from "no color field".
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Co-authored-by: Ariel Tobiana <arieltobiana@gmail.com>