feat(scum): add bounded vehicle spawn adapter

plugins/examples/scum-server-plugin/companion/UE4SS_CAPABILITY.md

@@ -17,6 +17,13 @@ that contract only for this exact source revision and UE4SS 3.0.1, with fixed
 chat type `4`; it cannot accept arbitrary RCON text. Its generated command
 text is private transport/audit data and never appears in a command result.
 
+The same pinned `ScumBridge::trim_command` implementation removes at most one
+leading `#` before dispatch. The authorized `vehicle.spawn` adapter preserves
+the required `#spawnvehicle <vehicleCode>` template internally, supplies it
+only to a Companion-local typed transport port, and never treats the source's
+raw response as a stable acknowledgement. Its isolated port fixture supplies
+the bounded success/failure/unknown receipt used by the adapter tests.
+
 ## Explicitly unavailable
 
 The reference contains no versioned server-side producer or documented API for:
@@ -27,6 +34,11 @@ The reference contains no versioned server-side producer or documented API for:
 - item/reward delivery; or
 - skill/attribute read, safe-window checking, or mutation.
 
+The fixed vehicle-spawn exception does not change these unavailable
+capabilities and does not authorize arbitrary RCON commands, arguments,
+targets, credentials, direct sockets, SQL, shell execution, or response
+projection.
+
 Therefore the Companion must not parse invented `LOGIN`/`LOGOUT` lines, upload
 semantic events, correlate network identifiers, or claim trajectory, reward,
 or game-state-patch support from this reference. The missing contract is a