[request] Matter over WiFi support (e.g. SiWx917-DK2605A)

[lboue]

Summary

The Matter implementation in this core currently only supports Matter over Thread (per the Matter library readme): a Thread Border Router is required to bridge the device to the rest of the network/WiFi.

Please add support for Matter over WiFi, using a WiFi-capable Silicon Labs SoC such as the SiWx917 (e.g. the SiWx917-DK2605A dev kit) as the target hardware.

Motivation:

• Not every user has (or wants to set up) a Thread Border Router - a lot of home networks are WiFi-only.
• The SiWx917 family is a WiFi + BLE SoC well suited to run the Matter stack directly over WiFi without needing a Thread mesh/border router at all, which would make commissioning and getting started significantly simpler for users who just have a regular WiFi router.
• It would let the Arduino Matter API (Matter, MatterLightbulb, MatterSwitch, etc.) target a second transport, alongside the existing Thread-based boards, the same way protocol_stack=matter already selects between build configurations per board in boards.txt.

Happy to help test on real hardware if useful.

[lboue]

For reference, Matter over Wi-Fi on SiWx917 already exists and is GA at the SDK level, so this shouldn't require a from-scratch implementation:

• SiliconLabs/matter — the underlying Matter stack already supports Wi-Fi SoC platform (SiWx917), GA and certifiable to CSA Matter 1.4.
• Simplicity Studio example: "Matter - SoC Lighting over Wi-Fi" for SiWx917 SOC (supported boards: BRD4325B/C/G) — docs.
• connectedhomeip reference example: closure-app/silabs runs Matter over Wi-Fi on SiWx917 today — BLE commissioning (Rendez-vous) followed by Wi-Fi join, same flow described in the Matter library readme for Thread but swapping the transport.
• Silicon Labs' own announcement: Develop Matter over Wi-Fi on the SiWx917.

Given this, adding SiWx917 support to this core would mainly be a matter of wiring a new board target in boards.txt (pointing protocol_stack=matter at the Wi-Fi variant of the underlying SDK/build config) rather than porting a new stack.