experimental/windivert: P2.1+P2.2 with WinDivert NETWORK+SOCKET layers

WIP snapshot before pivot to sing-box+TUN. Reached:
- TCP redirect via streamdump pattern (swap+Outbound=0+reinject)
- SOCKET layer for SYN-stage flow detection (avoids FLOW Establish-too-late race)
- Lazy PID→name resolution (catches Update.exe inside procscan tick)
- UDP forward via SOCKS5 UDP ASSOCIATE relay + manual reinject
- Result: chat works, voice times out (Discord IP discovery / RTC handshake fails)

Reason for pivot: WinDivert NAT-reinject pattern has subtle layer-3
semantics issues that DLL-injection / TUN-based proxies sidestep
entirely. Going with embedded sing-box + wintun as the engine —
proven path for Discord voice through SOCKS5.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/drover/debugflow_other.go

@@ -0,0 +1,12 @@
+//go:build !windows
+
+package main
+
+import (
+	"context"
+	"fmt"
+)
+
+func runDebugFlow(_ context.Context) error {
+	return fmt.Errorf("debug-flow requires Windows")
+}