1. [append it] append_file({"path": "log.txt", "text": "hello"}) -> already applied (resumed: this op landed before the previous run stopped)
2. finish -> appended

[transcript saved -> t1.txt]
1. [move it] move_file({"src": "a.txt", "dst": "b.txt"}) -> already applied (resumed: this op landed before the previous run stopped)
2. finish -> moved

[transcript saved -> t2.txt]
1. [append] append_file({"path": "x.txt", "text": "y"}) -> ERROR: a previous run stopped mid-op and left this path in an unknown state; refusing to re-apply
2. finish -> x

[transcript saved -> t3.txt]
PASS: append not doubled, move read as applied, unknown state refused