[user12xxxxxx]

What

Settings → Appearance → Typeface gains "Choose a font file…": pick any TTF or OTF on the phone through the system file picker (no new permission, no new dependency). The font is used for all text in the launcher.

• The file is copied to files/fonts/custom only after Typeface.Builder(file).build() confirms Android can load it. Anything else is refused with a toast ("That is not a TTF or OTF font") and the previous font stays.
• One slot: a new pick replaces the old font. Once imported, the font is listed by its file name in the Typeface dialog so you can switch back to it.
• FocusTheme falls back to the default face when the file is missing (for example after restoring settings on another phone), and Appearance then shows Sans.
• The split clock measures the custom font's "00:00" width instead of using the fixed sans/mono constants, so a wide font does not overflow its half.

Files

• ui/theme/CustomFont.kt (new): import, validate, load, measure
• data/Settings.kt: FontChoice.CUSTOM, customFontName
• ui/theme/Theme.kt, ui/home/HomeScreen.kt, ui/settings/LauncherPages.kt
• SettingsBackupTest: round-trips CUSTOM + name
• README and brain (3-details/ui-system.md, journal)

Limits

• One font file: light, medium and bold are synthesised by Compose unless the font has those weights itself.
• The font file is not part of the settings backup (a backup is one small JSON file).

Verified

• ./gradlew :app:testDebugUnitTest :app:lintDebug: 37 tests pass, lint 0 errors.
• Pixel 9 emulator (Android 17, debug build), through the system file picker: a TTF and an OTF each imported and showed in settings and on home, and the split clock fitted. A text file renamed .ttf was refused with the toast. With the stored file deleted, the app restarted in Sans with no crash.
• Not tested on a real phone, or with variable fonts.

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