tools: each module owns its Tool list, no duplication

Each tool module exports its own tools() returning Vec<Tool>.
mod.rs::tools() chains them. Individual _def() and handler functions
are pub(super), not exported. Aggregate definitions derived from
the Tool lists.

- memory: memory_tools(), journal_tools()
- channels: tools()
- control: tools()
- mod.rs: just chains + adds file/bash/web/vision

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/agent/tools/control.rs

@@ -50,7 +50,26 @@ pub(super) fn yield_to_user(args: &serde_json::Value) -> Result<ToolOutput> {
     })
 }
 
-pub(super) fn definitions() -> Vec<ToolDef> {
+pub(super) fn tools() -> Vec<super::Tool> {
+    use super::Tool;
+    let defs = definitions();
+    vec![
+        Tool { def: defs[0].clone(), // switch_model
+               handler: |_a, v| Box::pin(async move {
+                   let model = v.get("model").and_then(|v| v.as_str()).unwrap_or("");
+                   Ok(format!("Switching to model: {}", model))
+               }) },
+        Tool { def: defs[1].clone(), // pause
+               handler: |_a, _v| Box::pin(async { Ok("Pausing autonomous behavior. Only user input will wake you.".into()) }) },
+        Tool { def: defs[2].clone(), // yield_to_user
+               handler: |_a, v| Box::pin(async move {
+                   let msg = v.get("message").and_then(|v| v.as_str()).unwrap_or("(yielding to user)");
+                   Ok(msg.to_string())
+               }) },
+    ]
+}
+
+fn definitions() -> Vec<ToolDef> {
     vec![
         ToolDef::new(
             "switch_model",