Hide single-tab bar on Packs workspace view

When no pack is selected, the tab bar showed only one "Workspace" tab
which is pointless. Now tabs are conditionally rendered only when a
pack is opened (6 tabs: Dashboard, Edit, Rules, YAML, Approvals,
Simulate). Also removed urlParam="tab" to prevent double-navigation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Web/StellaOps.Web/src/app/features/policy-decisioning/policy-pack-shell.component.ts

@@ -54,15 +54,18 @@ const PACK_DETAIL_TABS: readonly StellaPageTab[] = [
         </div>
       </header>
 
-      <stella-page-tabs
+      @if (packId()) {
-        [tabs]="pageTabs()"
+        <stella-page-tabs
-        [activeTab]="activeSubview()"
+          [tabs]="pageTabs()"
-        urlParam="tab"
+          [activeTab]="activeSubview()"
-        ariaLabel="Pack tabs"
+          ariaLabel="Pack tabs"
-        (tabChange)="onTabChange($event)"
+          (tabChange)="onTabChange($event)"
-      >
+        >
+          <router-outlet />
+        </stella-page-tabs>
+      } @else {
         <router-outlet />
-      </stella-page-tabs>
+      }
     </section>
   `,
   styles: [`