feat: add a title icon to every labelled card

Add card.ICON and a card.title helper that draws the glyph in the
highlight colour before the label, at the label's own size. The eight
labelled cards use it, in both the fit_unit width measurement and the
draw, so the icon cannot overrun a narrow cell. Clock (no label) and
weather (condition glyph already) are unchanged, and the no-data notice
titles stay text-only.

Codepoints were chosen against a rendered contact sheet, not fontconfig
alone, since a wrong codepoint draws a plausible neighbour.

1 files changed, 4 insertions, 3 deletions

diff --git a/DESIGN.md b/DESIGN.md
index 34e8d95..b463c1f 100644
--- a/DESIGN.md
+++ b/DESIGN.md
@@ -73,6 +73,7 @@ One language for every measured quantity, so state is read rather than decoded:
 
 Nerd Font glyphs stand in for labels where an icon reads faster than a word:
 the disks rings put a distro / house / disk / network glyph at each ring's
-centre, weather puts the condition glyph in its header. A wrong-but-present
-codepoint draws a plausible neighbour rather than failing, so render a new
-glyph and look at it before trusting it.
+centre, weather puts the condition glyph in its header, and every card title
+carries one in `highlight` before its label (the codepoints live in
+`card.ICON`). A wrong-but-present codepoint draws a plausible neighbour rather
+than failing, so render a new glyph and look at it before trusting it.