* i18n tests: report missing translations instead of failing
The scans for untranslated menu strings, tl! literals, undo labels, menu labels and status
messages print what a complete language lacks. A missing translation shows the English
text until a translator adds the row, so it no longer fails the gate.
* i18n: one untranslated report in xtask ci; drop one-language wording tests
`i18n::tests::untranslated_report` lists, per language, the menu strings, tl! literals, undo
step names and templates, menu labels, render-site labels, status and error messages,
PostScript error meanings and default swatch names its catalog lacks; strings every language
lacks are listed once. It never fails on a gap, only on a scan that finds too few strings.
`cargo xtask ci` runs it in an `i18n-report` step, and `cargo xtask i18n-report` runs it alone.
The five scan tests, the render-site and swatch coverage tests and untranslated_messages.txt
fold into the report. Tests that pinned one language's wording are gone; where they also
checked code (lookups, plural rules, locale tags, menu and History step names, engine
parameter errors), that check stays and compares with the catalog lookup.
aiongg
cb06c7b34e