added optional schema for backwards compatibility

Author: ekang7

crates/chat-cli/src/cli/agent/mod.rs

@@ -129,6 +129,12 @@ pub enum AgentConfigError {
 #[serde(rename_all = "camelCase", deny_unknown_fields)]
 #[schemars(description = "An Agent is a declarative way of configuring a given instance of q chat.")]
 pub struct Agent {
+    #[serde(
+        rename = "$schema",
+        default = "default_schema",
+        skip_serializing_if = "String::is_empty"
+    )]
+    pub schema: String,
     /// Name of the agent
     pub name: String,
     /// This field is not model facing and is mostly here for users to discern between agents