feat: Mode Select (0x0050)

[simons-plugins]

What

Add a ModeSelectHandler for the Matter Mode Select cluster (0x0050). This is the generic multi-mode cluster used by devices that don't fit a more specific cluster — coffee makers, robot vacuums in simple form, smart appliances, multi-function sensors.

Matter details

• Cluster 0x0050 — Mode Select
• Key attributes: CurrentMode (0x0003, uint8), SupportedModes (0x0002, list of {label, mode, semanticTags}), StartUpMode (0x0004, optional), OnMode (0x0005, optional)
• Command: ChangeToMode {newMode: uint8}
• semanticTags provide machine-readable intent (e.g. MfgCode=0, Value=0 = "Auto"); without them the modes are device-specific text labels

Proposed Indigo mapping

• Device type: matterModeSelect — custom device
• State currentMode (integer) + currentModeLabel (string, derived from SupportedModes)
• Action: SelectMode with a dynamic list populated from SupportedModes labels
• SupportedModes stored as a plugin prop on first commission; refreshed on reconnect

Complexity note

SupportedModes is a variable-length list that must be read once and stored — it can't be statically declared in Devices.xml. The dynamic action list is the same challenge GenericSwitchHandler faces with event numbers. Precedent: thermostat fan-mode mapping already handles a small fixed enum; this is the generalised form.

Scope

Many appliance clusters (Laundry Washer Mode, Dishwasher Mode, Oven Mode, etc.) are thin wrappers around Mode Select semantics. A solid ModeSelectHandler would be the foundation for those if ever needed.