refactor(ui): simplify composer settings chip and animate chevron

Condense the settings-chip summary to quality, ratio, and image count
(dropping resolution and pixel size), wrap the label in an ellipsized
span, and swap the up/down chevron for a single rotating ChevronDown
across the canvas agent and image generator composers.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/ui/components/CanvasAgentComposer/index.css

@@ -242,11 +242,31 @@
 
 .composer-settings-chip {
   max-width: 150px;
-  padding: 0 8px;
+  gap: 2px;
+  padding: 0 4px 0 12px;
   overflow: hidden;
+  background: transparent;
   white-space: nowrap;
 }
 
+.composer-settings-chip span {
+  overflow: hidden;
+  font-size: 13px;
+  line-height: 20px;
+  text-overflow: ellipsis;
+}
+
+.composer-settings-chip svg {
+  width: 18px;
+  height: 18px;
+  flex: 0 0 auto;
+  transition: transform 150ms ease;
+}
+
+.composer-settings-chip svg.open {
+  transform: rotate(180deg);
+}
+
 .composer-icon-button,
 .composer-model-button {
   width: 32px;