Securexe Launcher v0.1.15

Add "remove from library" distinct from uninstall

New remove_from_library command: drops a slug from library.json and
reports a "removed" event to the worker, but never touches the actual
downloaded files (unlike uninstall, which does both). Gallery now shows
two small buttons per tile — the existing × (uninstall, destructive) and
a new − (remove from library, keeps the download) — sharing the same
click-twice-confirm interaction via a new makeConfirmButton helper.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>