fix: handle terminal install ops in install button

- Show uninstall (delete) actions immediately after install by treating Completed as not busy on the detail screen.
- Ignore stale Completed when the app is no longer installed so the primary CTA returns to Install.
- Allow install → uninstall → install again by clearing stale terminal ops (Completed/OperationFailed) in PackageManager.startDownload() (keeps batch progress UX intact).

lib/services/package_manager/package_manager.dart

@@ -330,7 +330,18 @@ abstract class PackageManager extends StateNotifier<PackageManagerState> {
     String? displayName,
   }) async {
     await _ensureDownloaderReady();
-    if (hasOperation(appId)) return false;
+    final existing = getOperation(appId);
+    if (existing != null) {
+      // We keep terminal states (Completed/Failed) in the operations map briefly so
+      // batch progress UI can derive totals. However, starting a new download for the
+      // same app should not be blocked by a stale terminal op (e.g. install -> uninstall
+      // -> install again). Only in-flight operations should block.
+      if (existing is Completed || existing is OperationFailed) {
+        clearOperation(appId);
+      } else {
+        return false;
+      }
+    }
 
     final downloadUrl = target.urls.firstOrNull;
     if (downloadUrl == null || downloadUrl.isEmpty) {

lib/widgets/install_button.dart

@@ -31,6 +31,12 @@ class InstallButton extends ConsumerWidget {
 
     // Derive what to display
     final isInstalled = installedPkg != null;
+    // Note: PackageManager keeps terminal operations (e.g. Completed) in the
+    // operations map for a while so batch UX (e.g. "All done") can derive counts.
+    // For the detail screen action row, Completed should be treated as "not busy"
+    // so the user can immediately Open/Delete after install.
+    final canShowActionButtons =
+        isInstalled && (operation == null || operation is Completed);
     final hasUpdate = app.hasUpdate;
     final hasDowngrade = app.hasDowngrade;
     final hasRelease = release != null;
@@ -76,7 +82,7 @@ class InstallButton extends ConsumerWidget {
           children: [
             Expanded(child: SizedBox(height: 48, child: button)),
             // Show action buttons only for installed apps with no active operation
-            if (isInstalled && operation == null) ...[
+            if (canShowActionButtons) ...[
               if (hasUpdate) ...[
                 const SizedBox(width: 8),
                 _buildOpenIconButton(context, ref),
@@ -101,9 +107,15 @@ class InstallButton extends ConsumerWidget {
     required FileMetadata? fileMetadata,
     required double fontSize,
   }) {
+    // Completed is a terminal "result" state and may linger for batch progress UX.
+    // If the app is no longer installed (e.g. user uninstalled right after install),
+    // ignore a stale Completed op so we fall back to the normal "Install" UI.
+    final effectiveOperation =
+        (!isInstalled && operation is Completed) ? null : operation;
+
     // Handle operation states first
-    if (operation != null) {
+    if (effectiveOperation != null) {
-      return switch (operation) {
+      return switch (effectiveOperation) {
         DownloadQueued() => _buildSimpleButton(
           context,
           'Queued for download',