Add BrokerPort: loopd asks brokerd for every tool call

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

crates/loopd/src/config.rs

@@ -136,6 +136,23 @@ impl Default for Baseline {
     }
 }
 
+/// The tool broker (`brokerd`). No socket means no broker: every non-core tool call fails.
+#[derive(Debug, Clone, PartialEq, Eq, Deserialize)]
+#[serde(deny_unknown_fields, default)]
+pub struct Broker {
+    pub socket: Option<std::path::PathBuf>,
+    pub timeout_ms: u64,
+}
+
+impl Default for Broker {
+    fn default() -> Self {
+        Self {
+            socket: None,
+            timeout_ms: 120_000,
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct Config {
@@ -154,6 +171,8 @@ pub struct Config {
     pub r#loop: Loop,
     #[serde(default)]
     pub baseline: Baseline,
+    #[serde(default)]
+    pub broker: Broker,
 }
 
 #[derive(Debug)]