fix(fuse): keep a move that lands while its create is read back (B161)

adopt_real_uid asked whether a move was queued only after reading the
node back. A move that landed in between left no op, and the answer still
had the old name, so the mount showed the file under it. Ask first.

The fake Drive can hold a read's answer (hold_answer_to_next_read) so the
test can land the move while the answer is on its way.

docs/BUGS.md

@@ -12,6 +12,31 @@ Conventions:
 
 ---
 
+## B161 — A file moved while it was being created shows up under its old name
+
+**Status:** Fixed.
+**Found:** 2026-10-04, by the simulation's slow-link profile (`one_client_on_a_slow_link`,
+seed 3). A file written and then moved at once ended up on Drive as `y/z/d`, but the mount
+showed it as `y/z/c.bin`, its name before the move, and `d` was missing.
+
+**Where:** `Core::adopt_real_uid` in `crates/pdfs-fuse/src/drain.rs`.
+
+**Cause.** A move made while a file's create is on the wire waits in the queue until the create
+lands. Once the create is retired, the drain reads the new node back from Drive and adopts it.
+The tree keeps the name the user gave only while the move is still queued. The drain asked
+about that after the read-back. On a slow link the move could land in between: the answer
+still had the old name, and the move was no longer queued, so the old name won.
+
+**Fix.** The drain asks whether a move is queued before it reads the node back. It still asks
+again under the tree's lock (B152).
+
+**Test:** simulation test `a_file_moved_while_its_create_was_on_the_wire_keeps_its_new_name`
+(failed before the fix: the new folder listed nothing). The fake Drive can now hold a read's
+answer, taken when the read arrives, until the test releases it
+(`FakeClient::hold_answer_to_next_read`).
+
+---
+
 ## B160 — A new folder reaches Drive only half a minute later
 
 **Status:** Fixed.