[Bug]: Extension finalize drops reservation pin before confirm

[dearsishs]

[Bug]: Extension finalize drops reservation pin before confirm

Description

When try_extend_reservation inline-finalizes an extension, it updates pending_confirms.reserved_until but not the reservation pin. Purge can delete the pin before the user confirms, forcing fallback to live commitment data.

Steps to reproduce

1. Reserve with pin at reserved_until=1000.
2. Inline finalize bumps deadline to 1300 at block 1001.
3. Pin purge removes stale pin; confirm uses live commitment.

Expected behavior

Pin reserved_until stays in sync with finalized extension target.

Actual behavior

Pin deleted; confirm path loses pinned reservation snapshot.