Add safe color controls

[wattsjus]

What changed

• add native --orange (#FF8000) and --purple (#E000A0) color commands
• on macOS, stop older blink1-tool processes before executing a new command
• wait briefly for an older process to release its HID handle before opening the device

Why

Continuous commands such as --playpattern keep running in their original process. A later invocation can set a new color, but the older animation then writes to the device again. This makes automation handoffs, such as moving from a pulsing Focus status to a solid meeting status, unreliable.

The macOS process handoff makes the newest invocation authoritative while retaining the existing command syntax. The two additional named colors provide convenient aliases consistent with the existing named-color options.

Impact

On macOS, invoking blink1-tool now terminates other processes named blink1-tool owned by any visible process entry before accessing the device. Other platforms retain their current process behavior.

Validation

• built successfully with CMake as a universal macOS binary
• tested --orange and --purple on a blink(1) mk3
• started an infinite purple --playpattern, then verified that blink1-tool --red terminated the older animation and left the light solid red
• ran git diff --check