A rewound turn's id is forgotten, so sending it again runs the turn anew

The turn log answered a repeated id with what that turn had answered, which
was right for a prompt sent twice over a dropped link and wrong for a turn
the web UI had just rewound to edit: the same id came back with the old
reply. rewind now returns the ids it took out, both handlers forget them from
the log, and the turn file drops them too, or the next load would have
brought them back.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/session/turns.ts

@@ -118,9 +118,10 @@ export class Turns {
   /** `_lembas/session/rewind`: the turn `turnId` and every later one leave the conversation the
    *  model sees and the history — their rows re-kinded as /undo re-kinds a turn's, the messages
    *  dropped — and the files are left as they are (the client says so beside its control). The
-   *  number of turns reverted, or undefined for a turn this session does not have. Not while a
-   *  prompt runs: the caller checks. */
-  rewind(turnId: string): number | undefined {
+   *  ids of the turns reverted, oldest first, or undefined for a turn this session does not have;
+   *  the caller forgets them from its turn log, or a client re-sending one would get the old
+   *  answer. Not while a prompt runs: the caller checks. */
+  rewind(turnId: string): string[] | undefined {
     const sessionId = this.engine.sessionId
     const i = this.done.findIndex((t) => t.turnId === turnId)
     if (i >= 0) {
@@ -130,20 +131,20 @@ export class Turns {
       this.engine.messages.splice(first.at)
       if (this.store && sessionId && last.lastRow >= first.firstRow) this.store.setKind(sessionId, first.firstRow, last.lastRow, "reverted")
       this.undone = []
-      return dropped.length
+      return dropped.map((t) => t.turnId)
     }
     // A turn run before this process had the session (opened from the store): by its row. Every
     // turn run here came after it, so they all go too.
     if (!this.store || !sessionId) return undefined
     const row = this.store.turnRow(sessionId, turnId)
     if (row === undefined) return undefined
-    const count = this.store.turnsFrom(sessionId, row)
+    const ids = this.store.turnIdsFrom(sessionId, row)
     this.store.setKind(sessionId, row, Number.MAX_SAFE_INTEGER, "reverted")
     const at = this.engine.messages.findIndex((m) => m.role === "user" && m.turnId === turnId)
     if (at >= 0) this.engine.messages.splice(at)
     this.done = []
     this.undone = []
-    return count
+    return ids
   }
 
   /** Everything changed since the session's first prompt, as a unified diff. */