feat: unify onboarding + config schema

docs/configuration.md

@@ -16,6 +16,14 @@ If the file is missing, CLAWDIS uses safe-ish defaults (embedded Pi agent + per-
 - tune the embedded agent (`agent`) and session behavior (`session`)
 - set the agent's identity (`identity`)
 
+## Schema + UI hints
+
+The Gateway exposes a JSON Schema representation of the config via `config.schema` for UI editors.
+The Control UI renders a form from this schema, with a **Raw JSON** editor as an escape hatch.
+
+Hints (labels, grouping, sensitive fields) ship alongside the schema so clients can render
+better forms without hard-coding config knowledge.
+
 ## Minimal config (recommended starting point)
 
 ```json5