#260 (fix attempt 2): static-width copy feedback via .swapbtn

internal/web/static/new.js

@@ -192,18 +192,16 @@ async function create() {
 // button, password auto-unlock, then redirect to the paste.
 function finishCreate(data) {
   const url = location.origin + '/' + (data.custom_slug || data.id);
-  showResult('<a href="' + url + '">' + url + '</a> <button class="btn btn-icon" id="result-copy" title="Copy URL" type="button">⧉</button>', 'ok');
+  // #260 attempt 2: .swapbtn markup — label and checkmark share one grid
+  // cell, so the button width is static and feedback is a class toggle.
+  showResult('<a href="' + url + '">' + url + '</a> <button class="btn btn-icon swapbtn" id="result-copy" title="Copy URL" type="button"><span class="swap-label">Copy</span><span class="swap-check">✓</span></button>', 'ok');
   $('result').dataset.token = data.deletion_token || '';
   const copyBtn = document.getElementById('result-copy');
   copyBtn.addEventListener('click', () => {
     try {
       navigator.clipboard.writeText(url);
       copyBtn.classList.add('ok');               // in-place success feedback (#53)
-      // #260: pin the pre-swap width so the wider/narrower glyph never
-      // shifts neighbouring elements; release it when the label restores.
-      copyBtn.style.minWidth = Math.ceil(copyBtn.getBoundingClientRect().width) + 'px';
-      copyBtn.textContent = '✓';
-      setTimeout(() => { copyBtn.classList.remove('ok'); copyBtn.textContent = '⧉'; copyBtn.style.minWidth = ''; }, 2000);
+      setTimeout(() => copyBtn.classList.remove('ok'), 2000);
     } catch(e) { toast('Copy failed', 'error'); }
   });
   // token carried via sessionStorage, never in the URL (#143)