feat(windows): WireGuard client, auto-VPN, IAM, tray enrichment, installer, CI

Second milestone of the Windows parity work (DESIGN-WINDOWS.md §13).

WireGuard mesh client (signed, WSS-delivered):
- wireguard_apply / wireguard_remove commands: Ed25519-verified, gated on a new
  wireguard capability. Linux applies via wg-quick up/down; Windows installs the
  peer config as a WireGuardTunnel service via wireguard.exe
  (/installtunnelservice, /uninstalltunnelservice)
- state polling in the home monitor drives the blue tray icon and auto-VPN:
  connect when away from home + auto_vpn, disconnect on return (2m cooldown)
- tray VPN toggle and the auto-VPN checkbox are now live; the preference
  persists to agent.yml (PersistAutoVPN)

IAM on Windows (iam_windows.go):
- allowed_login_groups -> net localgroup; ssh_keys -> per-profile
  authorized_keys + %ProgramData%\ssh\administrators_authorized_keys;
  revoke_users -> helper logs off all of the user's WTS sessions;
  sudo_rules logged as no direct equivalent

Tray enrichment:
- Open Config (opens agent.yml), Clear enrollment (re-enroll) menu items
- set_auto_vpn persists; vpn_connect/vpn_disconnect/reinit/open_config commands
  handled by the daemon (tray_server.go)

Packaging & release:
- installer/windows/installer.iss: fully-offline Inno Setup bundle (agent,
  tray, helper, vendor-signed WireGuard MSI, OpenCredential CP, VC++ redist),
  /SILENT /SERVER_URL /JOIN_KEY parameters, SYSTEM service + HKLM Run tray
  autostart, Users-writable %ProgramData%\Theta42 for the IPC socket
- .github/workflows/build-windows.yml: build + test, pinned vendor downloads,
  ISCC compile, Azure Trusted Signing (OIDC), SHA256SUMS, GH release attach,
  optional SSO resource publish
- agent.yml.example documents auto_vpn, wireguard, service_name,
  desktop_helper, public_ip_detect

Tests:
- wireguard_apply/remove dispatch (allowed + capability-denied), PersistAutoVPN,
  ClearEnrollment; dispatch tests pin linuxPlatformOps with a temp WireGuard conf
- end-to-end verified against a local mock SSO on Windows: join-key enrollment
  (token persisted, join key blanked), discovery/telemetry pushed, signed
  arbitrary_bash verified + executed via powershell -EncodedCommand; tray IPC
  socket binds %ProgramData%\Theta42; LDAP byte-pump binds 127.0.0.1:389;
  helper update swap verified

Rebuilds all tracked dist binaries (v2.1.0).

websocket.go

@@ -524,12 +524,53 @@ func handleCommand(cm *ConfigManager, msg WSMessage, c MessageWriter, exec Execu
 			return
 		}
 		log.Printf("Applying IAM revision %d for node %s...", payload.Revision, payload.NodeID)
-		if err := applyIAM(payload, exec); err != nil {
+		if err := defaultPlatformOps.ApplyIAM(payload); err != nil {
 			log.Printf("IAM apply failed: %v", err)
 			sendResponse("error", fmt.Sprintf("iam apply failed: %v", err))
 			return
 		}
 		sendResponse("ok", "iam applied")
+	case "wireguard_apply":
+		if !verifySignature(cfg, msg) {
+			sendResponse("error", "signature verification failed")
+			return
+		}
+		if !cfg.Capabilities.WireGuard {
+			log.Println("WireGuard apply rejected: capability disabled in agent.yml")
+			sendResponse("error", "wireguard capability disabled")
+			return
+		}
+		conf, _ := msg.Payload["config"].(string)
+		if conf == "" {
+			sendResponse("error", "missing wireguard config")
+			return
+		}
+		log.Printf("Applying WireGuard peer config...")
+		if err := defaultPlatformOps.ApplyWireGuard(conf); err != nil {
+			log.Printf("WireGuard apply failed: %v", err)
+			sendResponse("error", fmt.Sprintf("wireguard apply failed: %v", err))
+			return
+		}
+		SetVPNActive(true)
+		sendResponse("ok", "wireguard applied")
+	case "wireguard_remove":
+		if !verifySignature(cfg, msg) {
+			sendResponse("error", "signature verification failed")
+			return
+		}
+		if !cfg.Capabilities.WireGuard {
+			log.Println("WireGuard remove rejected: capability disabled in agent.yml")
+			sendResponse("error", "wireguard capability disabled")
+			return
+		}
+		log.Printf("Removing WireGuard tunnel...")
+		if err := defaultPlatformOps.RemoveWireGuard(); err != nil {
+			log.Printf("WireGuard remove failed: %v", err)
+			sendResponse("error", fmt.Sprintf("wireguard remove failed: %v", err))
+			return
+		}
+		SetVPNActive(false)
+		sendResponse("ok", "wireguard removed")
 	case "arbitrary_bash":
 		if !verifySignature(cfg, msg) {
 			sendResponse("error", "signature verification failed")