test: add gloss secondary commands test suite (red phase)

Six test files for the remaining stub commands. All 14 tests fail at
this commit because the implementations are stubs.

`gloss--add-finish-internal' (the pure save side of `gloss-add') gets
N/B/E coverage on validation and the persistence side effect.
`gloss--stats-text' (the pure stats string formatter) covers empty,
populated, and missing-file cases. The interactive commands
(`gloss-edit', `gloss-list-terms', `gloss-reload', `gloss-drill-export')
get smoke tests only — the design treats them as mode-glue with 70%
coverage targets, since prompts and `switch-to-buffer' are framework
behaviour Emacs already tests.

Two error-path tests assert the message contains a specific substring,
not just that `user-error' was raised. The stubs raise `user-error' too,
so a bare `should-error' would pass for the wrong reason. The substring
check anchors red against the real error path.

0 files changed, 0 insertions, 0 deletions