docs(gateway): clarify runtime settings registry

Signed-off-by: Taylor Mutch <taylormutch@gmail.com>

crates/openshell-server/src/runtime_config.rs

@@ -118,6 +118,8 @@ struct RawOpenShellRuntimeRoot {
 #[derive(Debug, Default, Deserialize)]
 #[serde(deny_unknown_fields)]
 struct RawRuntimeSection {
+    // Keep this as a key/value map so runtime config files use the same
+    // openshell_core::settings registry as CLI and gRPC settings writes.
     #[serde(default)]
     settings: BTreeMap<String, toml::Value>,
 }

docs/reference/gateway-config.mdx

@@ -161,7 +161,7 @@ ocsf_json_enabled = true
 proposal_approval_mode = "manual"
 ```
 
-Only registered runtime setting keys are accepted. The gateway rejects unknown keys, the reserved `policy` key, values with the wrong TOML type, and invalid enum strings.
+Only registered runtime setting keys are accepted. The runtime file accepts the same key names and value types as the global settings API. The gateway rejects unknown keys, the reserved `policy` key, values with the wrong TOML type, and invalid enum strings.
 
 When a runtime settings file is configured, keys present in that file are file-managed. `openshell settings set --global` and `openshell settings delete --global` reject changes to those keys; update the file instead. Keys omitted from the file remain managed through the normal global settings API. Removing a key from the file stops file-managing that key but does not delete the last persisted global value.