tools: add Tool registry with handlers

Tool struct wraps ToolDef + async handler function. tools() returns
the complete registry — single source of truth for definitions and
dispatch.

Handler signature: fn(Option<Arc<Mutex<Agent>>>, Value) -> BoxFuture<Result<String>>

All tools registered: file ops, bash, web, vision, memory (15 tools),
channels (4 tools), control (3 tools). Working stack removed from
registry (will be replaced).

Old dispatch functions remain for now — next step is to route
dispatch through the registry.

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

src/agent/tools/mod.rs

@@ -235,24 +235,63 @@ pub async fn dispatch_shared(
     })
 }
 
-/// Return all tool definitions (agent-specific + shared + memory).
+/// Return all registered tools with definitions + handlers.
+pub fn tools() -> Vec<Tool> {
+    vec![
+        // File tools
+        Tool { def: read::definition(),       handler: |_a, v| Box::pin(async move { read::read_file(&v) }) },
+        Tool { def: write::definition(),      handler: |_a, v| Box::pin(async move { write::write_file(&v) }) },
+        Tool { def: edit::definition(),       handler: |_a, v| Box::pin(async move { edit::edit_file(&v) }) },
+        Tool { def: grep::definition(),       handler: |_a, v| Box::pin(async move { grep::grep(&v) }) },
+        Tool { def: glob::definition(),       handler: |_a, v| Box::pin(async move { glob::glob_search(&v) }) },
+
+        // Execution tools
+        Tool { def: bash::definition(),       handler: |_a, v| Box::pin(async move { bash::run_bash(&v).await }) },
+        Tool { def: web::fetch_definition(),  handler: |_a, v| Box::pin(async move { web::web_fetch(&v).await }) },
+        Tool { def: web::search_definition(), handler: |_a, v| Box::pin(async move { web::web_search(&v).await }) },
+
+        // Vision
+        Tool { def: vision::definition(),     handler: |_a, v| Box::pin(async move { vision::view_image_text(&v) }) },
+
+        // Memory tools
+        Tool { def: memory::render_def(),     handler: |_a, v| Box::pin(async move { memory::render(&v) }) },
+        Tool { def: memory::write_def(),      handler: |_a, v| Box::pin(async move { memory::write(&v) }) },
+        Tool { def: memory::search_def(),     handler: |_a, v| Box::pin(async move { memory::search(&v) }) },
+        Tool { def: memory::links_def(),      handler: |_a, v| Box::pin(async move { memory::links(&v) }) },
+        Tool { def: memory::link_set_def(),   handler: |_a, v| Box::pin(async move { memory::link_set(&v) }) },
+        Tool { def: memory::link_add_def(),   handler: |_a, v| Box::pin(async move { memory::link_add(&v) }) },
+        Tool { def: memory::used_def(),       handler: |_a, v| Box::pin(async move { memory::used(&v) }) },
+        Tool { def: memory::weight_set_def(), handler: |_a, v| Box::pin(async move { memory::weight_set(&v) }) },
+        Tool { def: memory::rename_def(),     handler: |_a, v| Box::pin(async move { memory::rename(&v) }) },
+        Tool { def: memory::supersede_def(),  handler: |_a, v| Box::pin(async move { memory::supersede(&v) }) },
+        Tool { def: memory::query_def(),      handler: |_a, v| Box::pin(async move { memory::query(&v) }) },
+        Tool { def: memory::output_def(),     handler: |_a, v| Box::pin(async move { memory::output(&v) }) },
+
+        // Channel tools
+        Tool { def: channels::definitions()[0].clone(), handler: |_a, v| Box::pin(async move { channels::dispatch("channel_list", &v).await }) },
+        Tool { def: channels::definitions()[1].clone(), handler: |_a, v| Box::pin(async move { channels::dispatch("channel_recv", &v).await }) },
+        Tool { def: channels::definitions()[2].clone(), handler: |_a, v| Box::pin(async move { channels::dispatch("channel_send", &v).await }) },
+        Tool { def: channels::definitions()[3].clone(), handler: |_a, v| Box::pin(async move { channels::dispatch("channel_notifications", &v).await }) },
+
+        // Control tools
+        Tool { def: control::definitions()[0].clone(),
+               handler: |_a, _v| Box::pin(async { Ok("Pausing autonomous behavior. Only user input will wake you.".into()) }) },
+        Tool { def: control::definitions()[1].clone(),
+               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: control::definitions()[2].clone(),
+               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())
+               }) },
+    ]
+}
+
+/// Return all tool definitions (extracted from tools()).
 pub fn definitions() -> Vec<ToolDef> {
-    let mut defs = vec![
-        vision::definition(),
-        working_stack::definition(),
-        read::definition(),
-        write::definition(),
-        edit::definition(),
-        bash::definition(),
-        web::fetch_definition(),
-        web::search_definition(),
-        grep::definition(),
-        glob::definition(),
-    ];
-    defs.extend(control::definitions());
-    defs.extend(channels::definitions());
-    defs.extend(memory::definitions());
-    defs
+    tools().into_iter().map(|t| t.def).collect()
 }
 
 /// Return memory + journal tool definitions only.