[backport 1.26] refactor: Change manager flag from --disable-manager to --enable-manager (#5639)

Backport of #5635 to `core/1.26`

Automatically created by backport workflow.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5639-backport-1-26-refactor-Change-manager-flag-from-disable-manager-to-enable-manager-2726d73d36508120a29fcaefd91dbf40)
by [Unito](https://www.unito.io)

Co-authored-by: Jin Yi <jin12cc@gmail.com>

src/composables/useManagerState.ts

@@ -42,7 +42,12 @@ export function useManagerState() {
       )
 
       // Check command line args first (highest priority)
-      if (systemStats.value?.system?.argv?.includes('--disable-manager')) {
+      // --enable-manager flag enables the manager (opposite of old --disable-manager)
+      const hasEnableManager =
+        systemStats.value?.system?.argv?.includes('--enable-manager')
+
+      // If --enable-manager is NOT present, manager is disabled
+      if (!hasEnableManager) {
         return ManagerUIState.DISABLED
       }