Multi-mouse: support any Logitech HID++ mouse, several at once

[dpdev69]

Adds support for any Logitech HID++ 2.0 mouse with programmable buttons (REPROG_CONTROLS_V4), and for several mice at once: any mix of USB, Bluetooth and Unifying/Bolt/Nano receivers, including several mice on one receiver.

Draft: the multi-mouse code has not run on real hardware yet. Waiting on the hardware smoke test and the first CI run.

What changes

• Kit: support is decided by capability (HID++ ≥ 2.0, pointer kind, configurable controls on 0x1B04), not by model name or PID. Keyboards are excluded, and Lightspeed receivers are never opened. Other new pieces:
  • a device catalog, interface classifier and registry, with the same unit deduplicated across transports;
  • one hub per transport (HIDPPLink) and one EndpointController per mouse, with one request in flight per transport plus an interactive lane;
  • a remap engine that handles input from several mice;
  • mapping schema v3 with per-model tables. v2 data migrates into the MX Vertical model, and the v2 key is left untouched so a downgrade still works;
  • per-device preferences, and a public simulator under Simulation/.
• App:
  • a device manager that tracks every mouse, with pluggable device discovery (IOKit, or simulated mice for Demo Mode);
  • bindings per model and per-device actions (DPI, Easy-Switch, reconnect, forget);
  • a new Mice pane, a "Configure: [model]" picker in Buttons, one menu-bar row per mouse, and per-device battery alerts.
• Demo Mode: Upright --demo --export-snapshots <dir> and make snapshots render the real UI with three simulated mice into media/snapshots/. They never touch IOKit or the real defaults domain.
• Probe: upright-probe --all, read-only unless --divert is passed.
• Docs: README with a supported-devices table, docs/DEVICES.md, docs/HIDPP.md, CONTRIBUTING, CHANGELOG, and issue templates including a "new mouse" template. Only the MX Vertical is marked as verified on hardware.

Verification

• 388 UprightKit tests pass locally (Swift 6.4), including a 1000-step fuzz test of routing across several mice.
• make app (Release, universal) builds; hardened runtime and the macOS 13 deployment target are unchanged.
• The final audit had two Opus reviewers; each finding was then checked by a separate agent. 8 of the 9 findings are fixed. The ninth is this first CI run.
• Not verified yet:
  • Linux Swift 6.0 and Xcode 16.2 (this PR's CI);
  • real hardware: see docs/dev/HARDWARE-SMOKE-CHECKLIST.md. Section 4 matters most, because IOHIDManagerOpen is no longer called at launch;
  • models other than the MX Vertical, and two physical mice at once, have only been checked in the simulator.

Known limitations

These are listed in docs/dev/NEXT-STEPS.md under "Audit outcome":

• scroll settings apply to every mouse wheel;
• cursor-fallback gestures can't tell which mouse they came from;
• there are no app-target tests; only Kit tests exist.

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