fix: use MX Anywhere 3S layout key

[hieshima]

Problem

MX Anywhere 3S is already present in the Logitech device catalog, but its ui_layout is set to the image filename:

ui_layout="mouse_mx_anywhere_3s.png"

ui_layout is supposed to be a layout key, not an asset path. Because of this, an MX Anywhere 3S (0xB037) does not use the existing mx_anywhere_3s -> mx_anywhere family fallback and instead resolves to the generic mouse layout.

That means the device can be detected as MX Anywhere 3S while still losing the interactive Anywhere-family overlay.

Related context:

• Refs Add support for Logitech MX Anywhere 3S #12
• Related to [Bug] MX Anywhere 2S Middle Button is 1 Button (Should be @) #94, [Device] MX Anywhere 2S #96, feat: Support for Anywhere 2S model #98 as part of ongoing MX Anywhere-family support work

Fix

• Change MX Anywhere 3S ui_layout from the image filename to mx_anywhere_3s
• Keep image_asset="mouse_mx_anywhere_3s.png" unchanged
• Add regression coverage for Anywhere family layout fallback
• Add a catalog invariant test to prevent known device ui_layout values from silently being asset filenames or resolving to generic layouts

Scope

This is a static metadata fix only.

It does not change:

• HID++ runtime behavior
• button capability semantics
• unknown-device fallback policy
• QML/UI code
• config schema or migrations

It does not attempt to fix the MX Anywhere 2S button/capability issues tracked in #94/#96/#98.

Tested

uv run --with-requirements requirements.txt python -m unittest discover -s tests
Ran 265 tests in 23.217s
OK