Keyboard shortcuts for the web UI

Four shortcuts: `/` focuses the filter input, `r` triggers a library
rescan, `Esc` closes the topmost modal, `?` opens a help dialog
listing the bindings. All disabled while the focus is inside a text
input / textarea / contentEditable element so typing a video title
doesn't accidentally fire actions — except Esc, which always closes
modals (even from an input).

A new `?` button next to the existing rescan / maintenance / settings
icons makes the shortcuts discoverable; the help dialog is plain HTML
table with monospace key chips.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/web_ui/index.html

@@ -134,6 +134,7 @@
   <button onclick="rescan()" title="Rescan library">⟳</button>
   <button onclick="openStats()" title="Library statistics">📊</button>
   <button onclick="openMaintenance()" title="Library health">🩺</button>
+  <button onclick="showShortcutsHelp()" title="Keyboard shortcuts (?)">?</button>
   <button onclick="openSettings()">⚙</button>
   <span id="status"></span>
 </header>
@@ -1445,6 +1446,52 @@ function schedulePoll(ms){
 }
 schedulePoll(600);
 
+/* ── Keyboard shortcuts ─────────────────────────────────────────── */
+// Listed in the ? help dialog below. Skip when the user is typing in a
+// text input — otherwise pressing `r` while typing a filename would
+// trigger a rescan.
+document.addEventListener('keydown',(e)=>{
+  const tag=(document.activeElement?.tagName||'').toLowerCase();
+  const inField=tag==='input'||tag==='textarea'||document.activeElement?.isContentEditable;
+  // Esc always closes the topmost modal — even from within an input.
+  if(e.key==='Escape'){
+    const modals=document.querySelectorAll('.modal-bg');
+    if(modals.length){modals[modals.length-1].remove();e.preventDefault();return}
+  }
+  if(inField)return;
+  switch(e.key){
+    case '/':
+      document.getElementById('search')?.focus();
+      e.preventDefault();
+      break;
+    case 'r':
+      rescan();
+      e.preventDefault();
+      break;
+    case '?':
+      showShortcutsHelp();
+      e.preventDefault();
+      break;
+  }
+});
+function showShortcutsHelp(){
+  if(document.getElementById('shortcuts-help'))return;
+  const bg=document.createElement('div');bg.className='modal-bg';bg.id='shortcuts-help';
+  bg.onclick=e=>{if(e.target===bg)bg.remove()};
+  const row=(k,d)=>`<tr><td style="padding:4px 12px 4px 0"><kbd style="background:var(--card);border:1px solid var(--border);border-radius:3px;padding:1px 6px;font-family:monospace;font-size:11px">${k}</kbd></td><td style="padding:4px 0;font-size:13px">${d}</td></tr>`;
+  bg.innerHTML=`<div class="modal" style="max-width:380px">
+    <div class="modal-hdr"><h2>Keyboard shortcuts</h2><button onclick="this.closest('.modal-bg').remove()">✕</button></div>
+    <table><tbody>
+      ${row('/','Focus search')}
+      ${row('r','Rescan library')}
+      ${row('Esc','Close modal / cancel')}
+      ${row('?','This help')}
+    </tbody></table>
+    <div class="settings-hint" style="margin-top:10px">Shortcuts are ignored while typing in text inputs.</div>
+  </div>`;
+  document.body.appendChild(bg);
+}
+
 /* ── Utilities ──────────────────────────────────────────────────── */
 function fmtDur(s){s=Math.floor(s);const h=Math.floor(s/3600),m=Math.floor((s%3600)/60),sec=s%60;return h?`${h}:${p(m)}:${p(sec)}`:`${m}:${p(sec)}`}
 function fmtSize(b){if(b>=1073741824)return(b/1073741824).toFixed(1)+' GB';if(b>=1048576)return Math.round(b/1048576)+' MB';return Math.round(b/1024)+' KB'}