i18n: the message scan reads errors made with bad() and error variants, and new ones need rows

complete_languages_translate_every_message read a message literal only
right after a marker such as Err( or Other(. It did not read the
message given to the engine's bad(cmd, ...), so this test did not
require a row for a parameter error. It also did not read the messages
given to the engine's err() and error(), to the PDF writer's bad() and
failed(), or to an error enum's variant such as PsError::Limit(...).
1,122 of these messages have no row in any complete catalog.

The scan now reads those messages, a literal or a format! string, in
the same template form as the catalogs' rows. It skips PsError::Ps and
EngineError::UnknownCommand, whose first argument is a PostScript error
name or a command id. The 1,122 messages are listed in
untranslated_messages.txt next to the tests, together with the 71 that
pull requests open at 009384b add without rows, and the test lets a
listed message through whether or not it has rows. Every other message
needs a row in each complete catalog, so a new message made this way
fails the test until it has its rows.
VECTORCRAFT_I18N_DUMP_UNTRANSLATED=<file> writes the messages in the
sources that lack a row. No catalog rows change.

Docs: docs/development.md, docs/localization-parity.md.

docs/development.md

@@ -254,9 +254,14 @@ other `sv-*` locale resolve to it), Georgian (`ka`, complete; `ka-GE` and `ka_GE
   `Couldn't open {name}: {e}`; `{_1}`, `{_2}` … stand for the format string's `{}`, and the values in the
   placeholders are translated in turn (the reason after `: {e}` is often a message too). Czech, German, Greek, Spanish, French, Georgian, Hungarian, Italian, Japanese, Korean, Polish, Brazilian Portuguese, Russian, Simplified Chinese, Traditional Chinese, Swedish, Ukrainian, Vietnamese and Finnish cover every
   message literal the test scan finds (`complete_languages_translate_every_message`, languages listed in
-  `COMPLETE_MESSAGES`): a new `Err("…")`, `Other(…)`, `#[error(…)]` or `status(…)` message needs a row in each of those catalogs (`VECTORCRAFT_I18N_DUMP_MESSAGES=messages.txt cargo test -p vectorcraft-ui-egui
-  complete_languages_translate_every_message` lists them all). Other languages show messages in English
-  until they add `@msg` rows.
+  `COMPLETE_MESSAGES`), except the messages listed in `crates/ui-egui/src/i18n/untranslated_messages.txt`.
+  A new `Err("…")`, `Other(…)`, `#[error(…)]` or `status(…)` message needs a row in each of those catalogs, and so
+  does a new message given to an error enum's variant (`PsError::Limit(…)`), to the engine's `bad(cmd, …)`, `err(…)` or
+  `error(…)`, or to the PDF writer's `bad(…)` or `failed(…)` (`VECTORCRAFT_I18N_DUMP_MESSAGES=messages.txt cargo test -p vectorcraft-ui-egui
+  complete_languages_translate_every_message` lists them all). The list also holds the messages that open pull
+  requests add without those rows. A change that adds the rows for a listed message removes its line from the list
+  (`VECTORCRAFT_I18N_DUMP_UNTRANSLATED=<file>` writes the messages in the sources that lack a row). Other languages
+  show messages in English until they add `@msg` rows.
 - Not translated on purpose: names that are user data (layers, swatches, fonts, documents), the tab
   title's colour mode, command ids and parameter names inside messages. Not done yet: locale-aware number
   and date formats, right-to-left layout. Chinese and Japanese UI text