feat(ui): overhaul default channel editor with full param override visual editor

- Port classic ParamOverrideEditorModal to default as standalone dialog (~3200 lines)
  with two-panel layout, drag-to-reorder, 23 operation modes, template library,
  visual/JSON dual mode, conditions management, and legacy format support
- Redesign channel drawer layout with clear visual hierarchy (CardHeading vs SubHeading)
  and bordered sub-modules for Field Passthrough and Upstream Model Detection
- Replace header override JsonEditor with plain textarea matching classic behavior
- Add searchable channel type combobox with scroll fix
- Add 100+ i18n keys across all 6 locales (en, zh, fr, ja, ru, vi)

web/default/src/components/ui/combobox.tsx

@@ -103,7 +103,12 @@ export function Combobox({
           <ChevronsUpDown className='ml-2 h-4 w-4 shrink-0 opacity-50' />
         </Button>
       </PopoverTrigger>
-      <PopoverContent className='w-[var(--radix-popover-trigger-width)] p-0'>
+      <PopoverContent
+        className='w-[var(--radix-popover-trigger-width)] p-0'
+        onWheel={(e) => e.stopPropagation()}
+        onTouchMove={(e) => e.stopPropagation()}
+        onPointerDown={(e) => e.stopPropagation()}
+      >
         <Command shouldFilter={false}>
           <CommandInput
             placeholder={searchPlaceholder}