Expose `::part(dict-content)` on the MDict shadow content and add a
dictionary popup font-size setting (Settings → Language → Dictionaries),
independent of the main reading view.
- mdictProvider: tag the in-shadow body with `part="dict-content"` and a
stable `dict-shadow-host` class so the popup's `::part()` rule can reach
across the shadow boundary — MDict is the only provider that renders into
a shadow root, so ordinary popup CSS can't touch it.
- DictionarySettings.fontScale (default 1) with setFontScale + load-merge;
synced cross-device via the `dictionarySettings.fontScale` whitelist entry.
- DictionaryResultsView drives `--dict-font-scale` + `data-dict-content` on
each per-tab container. globals.css re-bases the light-DOM Tailwind text
utilities to `em` within that scope and sizes the MDict shadow body via
`::part(dict-content)`, so every provider scales from one lever.
- SettingsSelect control (85–175%) in the Dictionaries panel.
Tests: jsdom unit tests (part attribute, store fontScale, sync whitelist)
plus a real-Chromium browser test for the em-rebasing + `::part` + custom-
property-inheritance CSS contract jsdom cannot model.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Huang Xin
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