T25b Generative: queue and results

GenerationQueue shows each job's picture or where it stands, its
prompt and its progress, with Cancel, Retry and Remove as its state
allows; new rows fold in. GenerationGrid lays a run's results out in
their shape: breathing while they come, the picture once done, why one
failed with Retry. VariationPicker shows the chosen variation large
over thumbnails and ways on from it. ABCompareView sets two to four
models' answers side by side, blind until a verdict. ImageCompare
points to data_display::BeforeAfter.

primitives::framed and checked_ratio now serve previews and generative
alike. AGENTS.md records that gpui reads a &str picture as a web
address, and that grid rows overgrow tiles that keep a ratio.

src/primitives/mod.rs

@@ -18,6 +18,7 @@ pub(crate) use focus::{Takeover, give_back, hand_back, hold_focus, tab_stop, tak
 pub use ghost::DragGhost;
 pub use icon::{Icon, IconName};
 pub use image::Image;
+pub(crate) use image::{checked_ratio, framed};
 pub use measure::{IntersectionObserver, Measure};
 pub use pressable::Pressable;
 pub use severity::Severity;