Replaces the LINE Seed JP probe with Inter 18pt (Regular/Medium/
SemiBold/Bold static faces, compile-time embedded). Inter is a clean,
screen-tuned UI face; with the femtovg #5177/#11335 fixes it is the
candidate for the final look. FONT_TEST_INTER toggles back to the KDE
system font.
cc
Slint 1.14 has no public register_font API, so the .ttf is imported
in app.slint (compile-time embed + registration) and selected via the
FONT_TEST_LINESEED toggle in main.rs. Flip the toggle to false to
restore the KDE system font.
cc
vicrodh