fix(theme): per-skin legibility polish from the sweep review

Address the high-severity, systemic legibility issues found in the per-skin
screenshot review (verified across all 9 skins):

- Status pills (history): "Confirmed" text was 55%-alpha (dim); make it full
  opacity, and give status/shield pills a visible tinted fill (a48) + 1px border
  (a90) so they stop vanishing on dark-red / near-white / gradient skins.
- Console light theming: light skins now use a near-white terminal surface, and
  the log text/JsonBrace colors switch to the dark defaults in light themes (the
  schema colors are dark-terminal-authored — honor them only in dark themes) so
  text isn't pale-on-white.
- Dark-skin muted text: bump --on-surface-medium 0.85 / --on-surface-disabled
  0.58 on dragonx/dark/color-pop-dark/obsidian (obsidian addresses were ~1.1:1).
- Disabled Send button: the disabled fill was hardcoded white (invisible on
  light skins) — use a dark overlay in light themes.
- Light-skin inputs: stronger frame fill + border color and a 1px frame border
  for light themes so fields (and buttons) have defined boundaries on white/
  pastel surfaces.

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

src/ui/windows/send_tab.cpp

@@ -904,8 +904,12 @@ static void RenderActionButtons(App* app, float width, float vScale,
 
     // ---- Send button ----
     if (!can_send) {
-        ImGui::PushStyleColor(ImGuiCol_Button, ImGui::ColorConvertU32ToFloat4(IM_COL32(255, 255, 255, (int)S.drawElement("tabs.send", "disabled-btn-bg-alpha").size)));
-        ImGui::PushStyleColor(ImGuiCol_ButtonHovered, ImGui::ColorConvertU32ToFloat4(IM_COL32(255, 255, 255, (int)S.drawElement("tabs.send", "disabled-btn-bg-alpha").size)));
+        // The disabled fill must contrast the surface: a white overlay reads on dark skins but vanished
+        // on the light/pastel skins (white-on-white). Use a dark overlay for light themes.
+        int dAlpha = (int)S.drawElement("tabs.send", "disabled-btn-bg-alpha").size;
+        ImU32 disFill = IsLightTheme() ? IM_COL32(0, 0, 0, dAlpha) : IM_COL32(255, 255, 255, dAlpha);
+        ImGui::PushStyleColor(ImGuiCol_Button, ImGui::ColorConvertU32ToFloat4(disFill));
+        ImGui::PushStyleColor(ImGuiCol_ButtonHovered, ImGui::ColorConvertU32ToFloat4(disFill));
         ImGui::PushStyleColor(ImGuiCol_Text, ImGui::ColorConvertU32ToFloat4(OnSurfaceDisabled()));
     }