Let the agent set the merge commit title, defaulting to the task title

web/src/task.ts

@@ -125,7 +125,7 @@ export function mountTranscript(root: HTMLElement): () => void {
       confirmChanges(
         task,
         (u) =>
-          `Merge "${task.title}" into ${target}? The agent first merges ${target} in and resolves any conflicts; when that turn ends, ${changesText(u)} become one commit on ${target} and the task closes. Nothing is pushed.`,
+          `Merge "${task.title}" into ${target}? The agent first merges ${target} in and resolves any conflicts; when that turn ends, ${changesText(u)} become one commit on ${target} titled "${task.merge_title}", and the task closes. Nothing is pushed.`,
         async () => {
           await post("/api/tasks/{taskId}/merge", { path: { taskId: task.id } });
         },
@@ -700,6 +700,9 @@ function renderEvent(ev: ByreEvent, ctx: Ctx): HTMLElement | null {
       return null;
     }
 
+    case "task.merge_title":
+      return h("div", { class: "note" }, `${ev.actor} set the merge commit title to "${String(p["merge_title"])}" `, when);
+
     case "task.merged":
       return h("div", { class: "note" }, `${ev.actor} merged the task${p["commit"] ? ` as ${String(p["commit"]).slice(0, 7)}` : ""} `, when);