Add the tool port, registry, dispatch and the fake tools

Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)

crates/loopd/src/llama/mod.rs

@@ -26,7 +26,8 @@ pub enum ChatMessage {
     },
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, PartialEq, serde::Serialize, serde::Deserialize)]
+#[serde(deny_unknown_fields)]
 pub struct ToolSchema {
     pub name: String,
     pub description: String,