Dynamic subtitle and create button for Release Control tabs

- Title: "Release Control" (encompasses both tabs)
- Subtitle changes per tab:
  - Releases tab: "Promotion pipeline with gate status, risk posture, and evidence for every release."
  - Versions tab: "Sealed digest-first version catalog across standard and hotfix lanes."
- Create button changes per tab:
  - Releases tab: "New Release" → /releases/new
  - Versions tab: "New Version" → /releases/versions/new
- Uses Angular effect() to reactively update pageAction when activeTab changes

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

src/Web/StellaOps.Web/src/app/features/releases/releases-unified-page.component.ts

@@ -8,7 +8,7 @@
  * Tab 2 "Approvals": embeds the existing ApprovalQueueComponent.
  */
 
-import { Component, ChangeDetectionStrategy, OnInit, OnDestroy, ViewChild, inject, signal, computed } from '@angular/core';
+import { Component, ChangeDetectionStrategy, OnInit, OnDestroy, ViewChild, effect, inject, signal, computed } from '@angular/core';
 import { PageActionService } from '../../core/services/page-action.service';
 import { PageActionOutletComponent } from '../../shared/components/page-action-outlet/page-action-outlet.component';
 import { UpperCasePipe, SlicePipe } from '@angular/common';
@@ -74,8 +74,8 @@ export interface PipelineRelease {
     <div class="rup">
       <header class="rup__header">
         <div>
-          <h1 class="rup__title">Releases</h1>
-          <p class="rup__subtitle">Versions, deployments, approvals, and promotion pipeline.</p>
+          <h1 class="rup__title">Release Control</h1>
+          <p class="rup__subtitle">{{ activeSubtitle() }}</p>
         </div>
         <app-page-action-outlet />
       </header>
@@ -397,6 +397,24 @@ export class ReleasesUnifiedPageComponent implements OnInit, OnDestroy {
   readonly releaseTabs = RELEASE_TABS;
   readonly activeTab = signal<string>(this.route.snapshot.queryParamMap.get('tab') || 'releases');
 
+  readonly activeSubtitle = computed(() =>
+    this.activeTab() === 'versions'
+      ? 'Sealed digest-first version catalog across standard and hotfix lanes.'
+      : 'Promotion pipeline with gate status, risk posture, and evidence for every release.'
+  );
+
+  constructor() {
+    // Update page action when tab changes
+    effect(() => {
+      const tab = this.activeTab();
+      if (tab === 'versions') {
+        this.pageAction.set({ label: 'New Version', route: '/releases/versions/new' });
+      } else {
+        this.pageAction.set({ label: 'New Release', route: '/releases/new' });
+      }
+    });
+  }
+
   // Approve dialog
   readonly pendingApproveRelease = signal<PipelineRelease | null>(null);
   @ViewChild('approveConfirm') approveConfirmRef!: ConfirmDialogComponent;
@@ -426,7 +444,6 @@ export class ReleasesUnifiedPageComponent implements OnInit, OnDestroy {
   }
 
   ngOnInit(): void {
-    this.pageAction.set({ label: 'New Release', route: '/releases/new' });
     this.context.initialize();
     this.store.loadReleases({});
   }