feat(ui): enable drag-and-drop attachments and image previews in chat (#390)

* feat(BottomTerminalDock): add close button next to the fullscreen toggle in the dock

* style: replace hardcoded gradient with theme value in shine text variant

* fix(header): adapt instance button for desktop only

* refactor(chat): polish sticky turn UX and message action rows for better readability

Switch to stable sticky-only turn behavior and redesign user/assistant action controls (placement, hover rules, ordering, spacing, selection-safe clamp) to reduce visual noise and improve interaction flow.

* feat(chat/message): refactor buttons in messages footer

* feat: enhance image preview functionality in chat messages

- Added a new ImagePreviewDialog component to handle image previews with navigation support.
- Updated ToolOutputDialog to utilize the new ImagePreviewDialog for displaying images.
- Modified the ToolPopupContent type to include a gallery of images and an index for the current image.
- Removed the old inline image display logic from ToolOutputDialog.
- Improved file handling in the file store, including better MIME type guessing and handling of server paths.
- Introduced a new API endpoint for handling large session message payloads, allowing for better management of multi-file attachments.
- Updated the VSCode bridge to support session message requests with appropriate headers and body handling.

* feat(proxy): implement SSE forwarding and enhance generic API request handling

* feat(chat): support submitting only queued messages

* feat: add image preview transition state

* fix: default VSCode view to draft and fixed sessions list regression

packages/ui/src/components/layout/Header.tsx

@@ -882,19 +882,23 @@ export const Header: React.FC = () => {
                 <DropdownMenuTrigger asChild>
                   <button
                     type="button"
-                    aria-label={`Open instance, usage and MCP (current: ${currentInstanceLabel})`}
+                    aria-label={isDesktopApp
+                      ? `Open instance, usage and MCP (current: ${currentInstanceLabel})`
+                      : 'Open services, usage and MCP'}
                     className={cn(
                       headerIconButtonClass,
-                      'w-auto max-w-[14rem] justify-start gap-1.5 px-2.5'
+                      isDesktopApp
+                        ? 'w-auto max-w-[14rem] justify-start gap-1.5 px-2.5'
+                        : 'h-9 w-9'
                     )}
                   >
                     <RiStackLine className="h-5 w-5" />
-                    <span className="truncate text-base font-normal">{currentInstanceLabel}</span>
+                    {isDesktopApp && <span className="truncate text-base font-normal">{currentInstanceLabel}</span>}
                   </button>
                 </DropdownMenuTrigger>
               </TooltipTrigger>
               <TooltipContent>
-                <p>Current instance: {currentInstanceLabel}</p>
+                <p>{isDesktopApp ? `Current instance: ${currentInstanceLabel}` : 'Services'}</p>
               </TooltipContent>
             </Tooltip>
             <DropdownMenuContent