feat(agent): add Grok Build TUI adapter, runtime dispatch, and skill support

.mam.env.example

@@ -88,6 +88,10 @@
 #default: INFO
 # MAM_LOG_LEVEL=INFO
 
+# Optional xAI API Key for Grok Build CLI (if ~/.grok/auth.json is not present).
+#default: (unset → reads ~/.grok/auth.json)
+# XAI_API_KEY=replace_me
+
 # Retention period (days) for delegate-job event logs.
 #default: 7
 # MAM_EVENT_RETENTION_DAYS=7