Composite glass: inset highlights, blink, fade, panel tint

Closes the three "platform-impossible" gaps from the design audit
without resorting to hacks or shaders.

* chrome::glass — `render_inner_highlight(radius)` paints the design's
  `box-shadow: inset 0 0 0 1px` ring as an absolute overlay div with a
  1 px top-edge highlight sliver. GPUI 0.2.2's BoxShadow has no inset
  flag, so the composite is the only way to keep the panel content
  unclipped while the ring rides on top.
* chrome::animations — `blink` and `fade_in` wrap GPUI's first-class
  `with_animation` driver. Square-wave caret in the command header,
  180 ms opacity ramp on the command backdrop and workspace
  disclosure list.
* chrome::sidebar — panel_bg now tints toward the active wallpaper
  theme so the wallpaper bleeds through every glass surface, the
  closest honest substitute for backdrop-filter without a shader pass.
* command_overlay split: row helpers move to chrome::command_rows so
  command_overlay drops from 504 → 232 lines, well under the 500-line
  ceiling. No behavior change.

cargo test --workspace: 440 passed, 0 failed.

crates/ely_app/src/shell/render.rs

@@ -8,6 +8,7 @@ use gpui::{
 };
 
 use super::chrome::command_match::visible_command_rows;
+use super::chrome::glass::render_inner_highlight;
 use super::chrome::{
     panel_bg, panel_shadow, render_command_overlay,
     render_topbar as render_topbar_chrome, render_wallpaper,
@@ -136,6 +137,7 @@ impl ElyShell {
             .flex_1()
             .h_full()
             .min_w_0()
+            .relative()
             .flex()
             .flex_col()
             .rounded(px(spacing::RADIUS_CARD))
@@ -149,6 +151,7 @@ impl ElyShell {
                     .overflow_hidden()
                     .child(self.render_content_area(snapshot, active_tab, cx)),
             )
+            .child(render_inner_highlight(spacing::RADIUS_CARD))
             .into_any_element()
     }