Replaces the M4-placeholder stub with a real build/run guide covering prerequisites, build order (server → DLL → dotnet build), DLL dependency verification, manual test runbook, and the known limitations (focus-scoped PTT, NR passthrough, no admin UI, TOFU-pins-leaf-cert vs Ed25519). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>