Every colour the TUI painted on its own chrome was a named ratatui
colour spelled out at the use site, so nothing could be themed and the
selected card had broken contrast: the highlighted card's black-on-cyan
base was patched with an activity colour chosen for the dark card
background, leaving AwaitingInput yellow on light blue.
Roles now live in `palette.rs`, named for meaning. A palette holds one
role set per surface — card and selection — plus the panel border in
its focused and unfocused forms, a focus accent, a group-row style for
the sidebar grouping, the status-bar mode indicators and error text.
Each surface carries its own activity colours, so the selected card's
dot keeps carrying state without wearing a colour picked for another
background.
Values are `Color::Rgb`, so contrast is asserted rather than left to
the terminal theme: every role clears WCAG AA on its own surface, and a
sidebar test fails if a card-surface state colour is painted onto the
selection background.
PTY cell colours stay a passthrough of what the program in the pane
emits — they are not chrome and not a palette role.
Miguel Palhas
c534cee7cc