[clayzx]

Applications need composite values such as HH:mm:ss.SSS styled as one token. Styling individual time placeholders leaves separators uncolored; v5 removed the old addPlaceholders hook.

Adds pretty.placeholders callbacks resolved before native ANSI/CSS rendering, with styles under pretty.styles. Includes types, validation, child inheritance, callback failure isolation, documentation and tests.

Validation: All node tests, 100% coverage, 9 browser tests across Chromium/Firefox/WebKit, and manual WeChat Developer Tools verification.

[terehov]

Thanks @clayzx! Merged your commit (with your authorship) into #386, which adds a few follow-ups from review (numeric return values, runtime validation for pretty.styles keys, docs placement, bundle budget) and targets the development branch, where all PRs land. Closing this one in favor of #386.