Port the rumble packet from upstream driver/gamepad.c: a 9-byte
GIP_CMD_RUMBLE payload (motors R|L|RT|LT, intensities scaled to the
0..100 GIP range, duration/repeat constants). xone_controller_rumble
now sends it via client::send_rumble; the app button pulses both
motors for 0.6s then stops them. Completes the host to controller
TX remainder of Phase 3 (the dongle LED is already driven at chip
level for pairing and client lifecycle).
Co-Authored-By: qwen3.8-27b@q3_k_xl: implemented rumble TX
porterskyandqwen3.8-27b@q3_k_xl: implemented rumble TX
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