feat: close authored pulls with recovery (Closes #1356)

frontend/index.html

@@ -1792,6 +1792,20 @@
         <div id="pull-handoff-status" class="small" aria-live="assertive">Load teammates to transfer ownership.</div>
       </div>
     </details>
+    <details class="pull-lifecycle" id="pull-lifecycle" hidden>
+      <summary>Close pull request</summary>
+      <div>
+        <p class="small">Close an obsolete pull request without deleting its branch or discussion.</p>
+        <button id="close-authored-pull" type="button" hidden>Close pull request</button>
+        <div id="pull-lifecycle-status" class="small" role="status" aria-live="assertive"></div>
+      </div>
+    </details>
+    <section class="pull-close-receipt" id="pull-close-receipt" aria-labelledby="pull-close-receipt-title" hidden>
+      <h3 id="pull-close-receipt-title" tabindex="-1">Pull request closed.</h3>
+      <p class="small">This pull request was removed from active work. Reopen it if the close was accidental.</p>
+      <button id="reopen-authored-pull" type="button">Reopen pull request</button>
+      <div id="pull-reopen-status" class="small" role="status" aria-live="assertive"></div>
+    </section>
     <div class="pull-sheet-actions">
       <button class="share-work-route" type="button">Share</button>
       <button id="watch-pull-detail" type="button">Watch pull request</button>