Seven tasks (one infra + four descriptors + README + optional wiki
note). Each descriptor task ships JSON + images + test-fixture entry
in a single atomic commit. Every JSON is literal, every command is
exact, and each task has build + test verification before commit.

…elds

Make control6ActionType=nullptr and gestureDownPayload=nullptr signal
that a device has no 7th control or default gestures, respectively.
Prepares the fixture for the MX Anywhere family which has six controls
and no gesture button.

Bundled descriptor for the MX Anywhere 3S (Bluetooth PID 0xb037).
Logical data from Logitech Options+ extraction (jlevere/hidpp),
cross-checked against libratbag. Six controls: Left, Right, Middle,
Back, Forward, SmartShift toggle. No gesture button, no thumb wheel.
DPI 200-8000 step 50 per Logi spec sheet.

Hotspot positions and Easy-Switch slot coordinates ship as stubs at
(0.5, 0.5); maintainer polishes via 'logitune --edit' after merge.
Status: beta; pending hardware confirmation by the issue #46 tester.

Test fixture updated with one new DeviceSpec entry.

Closes #46

Same capabilities as MX Anywhere 3S. Bluetooth PID 0xb038.

PIDs 0xb025 (Bolt) and 0x4090 (Unifying). DPI 200-4000. Same
6-control layout as the 3S, without the extended DPI range or
pointerSpeed feature.

Same capabilities as MX Anywhere 3. Bolt PID 0xb02d. Uses its own
front/side images from the reference repo (different branding from
the consumer variant).

Four rows for MX Anywhere 3, 3 for Business, 3S, 3S for Business.
All marked beta pending hardware confirmation tracked in #46.

… CIDs

Prevents contributors from adding 0x00d7 as a control when the device
has a top-side connection switch button. Firmware handles the button
via the multi-host mechanism already.

QML consumers match hotspots by kind ("scrollwheel", "thumbwheel",
"pointer"). The field was populated on the C++ side but dropped when
converting to QVariantMap, causing callouts and markers to fall back to
hardcoded percentages and drift away from the descriptor hotspot.

Add DeviceModel::thumbWheelSupported (reads descriptor feature flag,
default true for safety). PointScrollPage now hides the thumb-wheel
callout on mice that do not have one, so mice like the MX Anywhere
family render only the scroll wheel and pointer speed callouts.

…n mode

Three related improvements to the Easy-Switch page:

- Device back image aspect is now read from the loaded PNG instead of
  being hard-coded to the MX Master ratio (0.676). Landscape shots such
  as the MX Anywhere bottom view no longer shrink to portrait size.
- Slot circles scale with the rendered image height so they stay the
  same visual size across mice and window sizes.
- In run mode, only the active slot's circle is drawn. Inactive slots
  are marked by the device's own printed labels. Edit mode still shows
  all circles with numbered labels so positions can be tuned.

…tions

Back-view PNG for each MX Anywhere variant so the Easy-Switch page
renders the correct bottom shot with the three channel indicators.

Slot and scroll/pointer hotspot percentages updated from an in-app
editor session so the overlays line up on the new back image and the
existing side image.