The mobile git sheet and quick action only read the PR derived from the
checked-out ref, so a thread-linked PR on another ref (a fork branch, a
stacked layer) had no open-PR action. Fold the thread's current open link
into the status, treating an unsynced link as open.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Signed-off-by: Tiger Kaovilai <passawit.kaovilai@gmail.com>