i18n: shipped components read their copy from the catalog

Select's default placeholder, the clear, close, remove and unpin tooltips,
the completion menu's empty line and the size sample showed English under
zh-CN. A source test now fails on any fixed English literal in them.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/i18n/tests/mod.rs

@@ -2,8 +2,9 @@ use jiff::{Timestamp, tz::TimeZone};
 
 use super::{Direction, I18n, LOCALES, Locale, fill};
 
-#[cfg(feature = "test-support")]
 mod a11y;
+#[cfg(feature = "test-support")]
+mod shipped;
 
 fn i18n() -> I18n {
     I18n::new("en-US")