docs: document usb mavlink and configurator startup

docs/src/architecture.md

@@ -61,11 +61,12 @@ erase sectors, retaining only the old and replacement records across the commit
 boundary. Neither format is exposed as the public KCFG file.
 Motor allocation/mixer topology is immutable compiled vehicle capability data,
 never a scalar field or persistence member. F722 recovers operational settings
-before constructing consumers. Its directly wired local UART accepts only
-exact-target, CRC-valid Kaptan file requests while physical outputs remain
-inhibited. CRC is integrity-only; a shared or remote GCS still needs production
-authentication, source binding, and persistent anti-replay state. Disarmed
-activation and flight-consumer reconstruction remain separate reviewed work.
+before constructing consumers. Its local USB CDC-ACM and directly wired UART
+accept only exact-target, CRC-valid Kaptan file requests while physical outputs
+remain inhibited. CRC is integrity-only; a shared or remote GCS still needs
+production authentication, source binding, and persistent anti-replay state.
+Disarmed activation and flight-consumer reconstruction remain separate reviewed
+work.
 
 The MAVLink dialect root directly includes one-message XML leaves under
 `publish/` and `transfer/`. The `exchange/` contract remains empty until a