loopd: subagent in the M5c registry, not core

Co-Authored-By: ornith-1.5-35b-a3b <agent@wntrmute.dev>

crates/loopd/src/lib.rs

@@ -15,6 +15,7 @@ pub mod selftest;
 pub mod session;
 pub mod socket;
 pub mod sse;
+pub mod subagent;
 pub mod summarise;
 pub mod tools;
 pub mod turn;

crates/loopd/src/subagent.rs

@@ -0,0 +1,22 @@
+//! The `subagent` tool: loopd answers it itself (M6 spec, section 3).
+//! It is not core; the parent finds it with `find_tool` and calls it through `call_tool`.
+
+pub const SUBAGENT: &str = "subagent";
+
+pub fn schema() -> crate::llama::ToolSchema {
+    crate::llama::ToolSchema {
+        name: SUBAGENT.to_string(),
+        description: "Run a short task in an isolated child session on the background slot."
+            .to_string(),
+        parameters: serde_json::json!({
+            "type": "object",
+            "properties": {
+                "task": {
+                    "type": "string",
+                    "description": "What the child should do."
+                }
+            },
+            "required": ["task"]
+        }),
+    }
+}

crates/loopd/src/tools.rs

@@ -114,6 +114,10 @@ impl Registry {
                 core: true,
             },
         );
+        entries.push(Entry {
+            schema: crate::subagent::schema(),
+            core: false,
+        });
         Registry::new(entries)
     }