Convert chrome-local color constants to theme-aware accessors

The previous theme refactor only flipped `colors::*` tokens; the
~50 chrome-local `const FOO: u32 = 0xffffff…;` overlays kept their
white-glass values, so dark mode still painted a light omnibar pill,
light search field, light sidebar tab card, light command-overlay
backdrop, light sync page chips, etc.

Promote `colors::pick(light, dark)` to `pub` so component-internal
constants can reach the same thread-local mode the global palette
uses, then convert every white-glass (`0xffffff??`) and warm-dark
wash (`0x281e14??`) constant in:

- chrome/topbar (omnibar pill, hover chip)
- chrome/sidebar_chrome + chrome/sidebar (rail nav row hover/active,
  highlight border, close-button hover, unread badge)
- chrome/sidebar_header (workspace picker, disclosure card)
- chrome/command_overlay + chrome/command_rows + chrome/command_footer
- chrome/settings_layout, chrome/appearance_form,
  chrome/appearance_layout_cards, chrome/plugin_detail_view
- chrome/home/style (search field, arrow chip, pill, card, add-tile)
- internal_pages/sync (status pill, metrics card, button row)
- internal_pages/plugin_catalog
- shell/render (main pane highlight border)

Each constant becomes `fn name() -> u32 { colors::pick(<light>, <dark>) }`
where the dark counterpart preserves the original alpha but swaps the
warm-white prefix `ffffff` for warm-graphite `1f1d1b` (or the inverse:
`281e14` warm-dark wash → `f2efe9` warm-white wash). Brand accents
(`0xc96442??`, `0xffaa7733`) and the global slate backdrop keep their
single value across modes.

crates/ely_app/src/shell/chrome/command_overlay.rs

@@ -45,7 +45,7 @@ fn render_overlay(
         div()
             .absolute()
             .inset_0()
-            .bg(rgba(BACKDROP_BG))
+            .bg(rgba(backdrop_bg()))
             .flex()
             .flex_col()
             .items_center()
@@ -67,9 +67,9 @@ fn render_panel(
     div()
         .w(px(640.0))
         .rounded(px(16.0))
-        .bg(rgba(PANEL_BG))
+        .bg(rgba(panel_bg()))
         .border_1()
-        .border_color(rgba(PANEL_BORDER))
+        .border_color(rgba(panel_border()))
         .shadow(panel_shadow())
         .overflow_hidden()
         .flex()
@@ -111,7 +111,7 @@ fn render_header(query_label: String, is_empty: bool) -> AnyElement {
                 .px(px(8.0))
                 .py(px(2.0))
                 .rounded(px(6.0))
-                .bg(rgba(BADGE_BG))
+                .bg(rgba(badge_bg()))
                 .text_size(px(10.5))
                 .text_color(rgb(colors::ink_3()))
                 .child("Switcher"),
@@ -199,10 +199,18 @@ fn render_empty_state() -> AnyElement {
         .into_any_element()
 }
 
-const PANEL_BG: u32 = 0xfffffff5;
-const PANEL_BORDER: u32 = 0xffffff80;
-const BACKDROP_BG: u32 = 0x140f0a3d;
-const BADGE_BG: u32 = 0x281e140f;
+fn panel_bg() -> u32 {
+    colors::pick(0xfffffff5, 0x1f1d1bf5)
+}
+fn panel_border() -> u32 {
+    colors::pick(0xffffff80, 0x1f1d1b80)
+}
+fn backdrop_bg() -> u32 {
+    colors::pick(0x140f0a3d, 0x0d0c0a3d)
+}
+fn badge_bg() -> u32 {
+    colors::pick(0x281e140f, 0xf2efe90f)
+}
 
 fn panel_shadow() -> Vec<BoxShadow> {
     vec![BoxShadow {