Add ready_for_merge tool and prompt agents for it after review

mac/Sources/Byre/TranscriptBuilder.swift

@@ -51,6 +51,7 @@ enum RowKind {
     case turnEnd(error: String?)
     case note(Note)
     case review(note: Note, md: [MDBlock])
+    case ready(when: Date, md: [MDBlock])
     case handoff
     case snapshot(Snapshot)
     case question
@@ -192,6 +193,7 @@ final class TranscriptBuilder {
     private(set) var context: [String: Usage] = [:]
     private(set) var open = false
     private(set) var lastMergeAfterReview: Int?
+    private(set) var lastReady: Int?
     @ObservationIgnored private var ctx = Ctx()
     @ObservationIgnored private var sink: RowList?
     @ObservationIgnored private var stream: Row?
@@ -460,6 +462,9 @@ final class TranscriptBuilder {
                 let snap = try! decodePayload(ev.payload, as: Snapshot.self)
                 let row = Row(.snapshot(snap), taskId: taskId)
                 ctx.reviewButtons[snap.n] = row
+                if snap.trigger != .answer && sink == nil {
+                    lastReady = nil
+                }
                 put(row)
                 continue
             }
@@ -540,6 +545,9 @@ final class TranscriptBuilder {
             if ev.kind == "task.merge_after_review" && sink == nil {
                 lastMergeAfterReview = row.id
             }
+            if ev.kind == "task.ready" && sink == nil {
+                lastReady = row.id
+            }
             put(row, keepHeld: ev.kind == "agent.thinking")
         }
         return contextChanged
@@ -744,6 +752,9 @@ final class TranscriptBuilder {
         case "task.summary":
             return note([.text("\(ev.actor) set the task summary")])
 
+        case "task.ready":
+            return Row(.ready(when: when, md: parseMarkdown(jsString(p["overview"]))), taskId: taskId)
+
         case "task.discard_started":
             return note([.text("\(ev.actor) asked to discard the task; the agent writes the task summary first")])