Update project dependencies and configurations; remove deprecated package settings and enhance legacy build support

- Upgrade package manager to pnpm@11.5.2 and remove patched dependencies from package.json.
- Update pnpm-lock.yaml to reflect new dependency versions and remove obsolete entries.
- Refactor Vite configuration to improve legacy build handling, including new plugins for legacy CSS management.
- Remove unused client/index.html file and adjust paths in Vite config for better project structure.
- Enhance DesktopAIShell and EQPage components to support legacy build conditions and improve loading states for raw curves.

client/src/components/DesktopAIShell.tsx

@@ -65,6 +65,8 @@ function SplitDivider({
   );
 }
 
+const isLegacyBuild = import.meta.env.VITE_X8_LEGACY === "1";
+
 /**
  * lg+: optional side-by-side AI panel with draggable divider. Mobile unchanged (router only).
  */
@@ -87,7 +89,9 @@ export default function DesktopAIShell({ children }: { children: ReactNode }) {
         "w-full min-w-0",
         showSplit
           ? "flex h-dvh max-h-dvh flex-row overflow-hidden"
-          : "min-h-dvh",
+          : isLegacyBuild
+            ? "min-h-0"
+            : "min-h-dvh",
       )}
     >
       <div
@@ -97,7 +101,9 @@ export default function DesktopAIShell({ children }: { children: ReactNode }) {
             ? "h-full min-h-0 overflow-y-auto overflow-x-hidden"
             : isLgUp
               ? "min-h-dvh overflow-x-hidden"
-              : "min-h-dvh max-h-dvh overflow-x-hidden overflow-y-auto overscroll-y-contain [touch-action:pan-y]",
+              : isLegacyBuild
+                ? "w-full overflow-x-hidden"
+                : "min-h-dvh max-h-dvh overflow-x-hidden overflow-y-auto overscroll-y-contain [touch-action:pan-y]",
         )}
         style={
           showSplit