fix(util): format collapsibleDate time without locale dependency (#1603)

* fix(util): format collapsibleDate time without locale dependency (#1494)

* fix: remove unused timeWithUnnecessarySeconds regex

* test: cover collapsibleDate under a 24-hour default locale

Stub the default toLocaleTimeString to a de-DE format so the
regression for #1494 is exercised regardless of the machine's locale.

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

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Co-authored-by: David Blass <david@arktype.io>
Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>