fix(latex): make PDF-viewer selection idempotent

cj/--latex-select-pdf-viewer runs on every LaTeX-mode buffer and was blindly pushing an (output-pdf VIEWER) entry onto TeX-view-program-selection, so each LaTeX buffer opened in a session stacked another duplicate. The head still won, so the viewer worked, but the list grew and the docstring's idempotency claim was false. I drop any existing output-pdf entry before consing the chosen viewer, which also makes "wins over any default" actually true.

Added a test file (the module had none) covering selection, preference order, the PDF-Tools fallback, idempotency, and default override, with executable-find mocked so the run doesn't depend on which viewers are installed.

0 files changed, 0 insertions, 0 deletions