The PASTE column fallback for untitled pastes used the .slug class, which
renders as a monospace chip with a background pill. Give it a dedicated
paste-name modifier that strips the chip styling (background, padding,
radius, mono font) so the fallback looks identical to a titled paste
(var(--fg) plain text). The dedicated ID column and URL column chips keep
their existing styling. Applied to both /history and /mine tables.