Add Windows VHF Precision Touchpad bridge

[fakebob2004]

What changed

• add a strict MTP1 TCP receiver with contact lifecycle and timeout handling
• add a KMDF/VHF source driver exposing a five-contact Windows Precision Touchpad
• install the required in-box vhf.sys lower filter through the INF
• add fixed-size IOCTL ABI, feature reports, diagnostic counters, and a synthetic touch sender
• add parser/session tests and open-source reuse notes
• add a macOS handoff guide for the first real-trackpad integration

Why

This completes the Windows half of the remote MacBook trackpad bridge. The
original source device failed in VhfCreate because the INF linked
vhfkm.lib but did not install vhf.sys as a lower filter. The corrected
stack now enumerates a HID-compliant Precision Touchpad and accepts reports
from the receiver.

Validation

• mtp-tests: ok
• Inf2Cat: 0 errors, 0 warnings
• test-signed SYS and CAT validated, including catalog membership
• root device, vhf lower filter, and VHF child all start without PnP errors
• Windows selects input mode 3 and function mask 0x3
• diagnostic run: 50-byte reports, VhfReadReportSubmit = STATUS_SUCCESS
• corrected Scan Time and Confidence handling; synthetic single-contact input
  moves the Windows pointer

Remaining work

• run the existing macOS agent against the Windows receiver using
  docs/MAC_HANDOFF.md
• validate real multi-finger gestures, reconnect, sleep/wake, and long-duration
  behavior
• add pairing/TLS and service/installer packaging if the project moves beyond
  trusted-LAN personal use