options.lua is a whole-file rewrite, so a caller handing saveOptions a
partial table (only the keys it changed) silently dropped every key it did
not mention: launcher-only keys like lastVersion, and keys the launcher set
(battleBg, tilt) all fell back to defaults.
saveOptions now reads the on-disk file first and folds caller-absent
values underneath before mergeOptions backfills defaults. A table holding
every defaultOptions key is a full snapshot and stays authoritative, so the
fold is inert for all in-repo writers (every one passes loadOptions-ed
tables) and cannot resurrect the bindings/activeProfile deletions the
RESET REBINDS and mod-manager paths make on full tables.
Adds a regression suite (options_partial_write_bug932.lua) pinning the
merge, and updates the #828 suite's partial-write assertion, which now
expects lastVersion to survive a delta write.
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Shane McGovern