feat: notification sound and browser notifications on task completion

Add two new settings (both default off):
- sound_enabled: plays a short tone via Web Audio API when assistant
  finishes a response or requests approval
- notifications_enabled: shows a browser notification when a response
  completes while the tab is in the background

Uses Web Audio API (oscillator) instead of bundled MP3 file — zero
additional assets. Follows the standard 4-file settings pattern.

Also skip test_valid_skill_accepted when hermes-agent not installed
(skills endpoint returns 500 without the agent module).

Inspired by #176 (DavidSchuchert)

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

static/boot.js

@@ -322,7 +322,7 @@ function applyBotName(){
 (async()=>{
   // Load send key preference
   let _bootSettings={};
-  try{const s=await api('/api/settings');_bootSettings=s;window._sendKey=s.send_key||'enter';window._showTokenUsage=!!s.show_token_usage;window._showCliSessions=!!s.show_cli_sessions;window._botName=s.bot_name||'Hermes';const _theme=s.theme||'dark';document.documentElement.dataset.theme=_theme;localStorage.setItem('hermes-theme',_theme);applyBotName();}catch(e){window._sendKey='enter';window._showTokenUsage=false;window._showCliSessions=false;window._botName='Hermes';_bootSettings={check_for_updates:false};}
+  try{const s=await api('/api/settings');_bootSettings=s;window._sendKey=s.send_key||'enter';window._showTokenUsage=!!s.show_token_usage;window._showCliSessions=!!s.show_cli_sessions;window._soundEnabled=!!s.sound_enabled;window._notificationsEnabled=!!s.notifications_enabled;window._botName=s.bot_name||'Hermes';const _theme=s.theme||'dark';document.documentElement.dataset.theme=_theme;localStorage.setItem('hermes-theme',_theme);applyBotName();}catch(e){window._sendKey='enter';window._showTokenUsage=false;window._showCliSessions=false;window._soundEnabled=false;window._notificationsEnabled=false;window._botName='Hermes';_bootSettings={check_for_updates:false};}
   // Non-blocking update check (fire-and-forget, once per tab session)
   // ?test_updates=1 in URL forces banner display for testing (bypasses sessionStorage guards)
   const _testUpdates=new URLSearchParams(location.search).get('test_updates')==='1';

static/index.html

@@ -345,6 +345,20 @@
           <option value="oled">OLED</option>
         </select>
       </div>
+      <div class="settings-field">
+        <label style="display:flex;align-items:center;gap:8px;cursor:pointer">
+          <input type="checkbox" id="settingsSoundEnabled" style="width:15px;height:15px;accent-color:var(--accent)">
+          Notification sound
+        </label>
+        <div style="font-size:11px;color:var(--muted);margin-top:4px">Play a sound when the assistant finishes a response.</div>
+      </div>
+      <div class="settings-field">
+        <label style="display:flex;align-items:center;gap:8px;cursor:pointer">
+          <input type="checkbox" id="settingsNotificationsEnabled" style="width:15px;height:15px;accent-color:var(--accent)">
+          Browser notifications
+        </label>
+        <div style="font-size:11px;color:var(--muted);margin-top:4px">Show a system notification when a response completes while the tab is in the background.</div>
+      </div>
       <div class="settings-field">
         <label style="display:flex;align-items:center;gap:8px;cursor:pointer">
           <input type="checkbox" id="settingsShowTokenUsage" style="width:15px;height:15px;accent-color:var(--accent)">

static/messages.js

@@ -143,6 +143,8 @@ async function send(){
       const d=JSON.parse(e.data);
       d._session_id=activeSid;
       showApprovalCard(d);
+      playNotificationSound();
+      sendBrowserNotification('Approval required',d.description||'Tool approval needed');
     });
 
     source.addEventListener('done',e=>{
@@ -176,6 +178,8 @@ async function send(){
         syncTopbar();renderMessages();loadDir('.');
       }
       renderSessionList();setBusy(false);setStatus('');
+      playNotificationSound();
+      sendBrowserNotification('Response complete',assistantText?assistantText.slice(0,100):'Task finished');
     });
 
     source.addEventListener('compressed',e=>{
@@ -360,5 +364,36 @@ function startApprovalPolling(sid) {
 function stopApprovalPolling() {
   if (_approvalPollTimer) { clearInterval(_approvalPollTimer); _approvalPollTimer = null; }
 }
+
+// ── Notifications and Sound ──────────────────────────────────────────────────
+
+function playNotificationSound(){
+  if(!window._soundEnabled) return;
+  try{
+    const ctx=new (window.AudioContext||window.webkitAudioContext)();
+    const osc=ctx.createOscillator();
+    const gain=ctx.createGain();
+    osc.connect(gain);gain.connect(ctx.destination);
+    osc.type='sine';osc.frequency.setValueAtTime(660,ctx.currentTime);
+    osc.frequency.setValueAtTime(880,ctx.currentTime+0.1);
+    gain.gain.setValueAtTime(0.3,ctx.currentTime);
+    gain.gain.exponentialRampToValueAtTime(0.01,ctx.currentTime+0.3);
+    osc.start(ctx.currentTime);osc.stop(ctx.currentTime+0.3);
+  }catch(e){console.warn('Notification sound failed:',e);}
+}
+
+function sendBrowserNotification(title,body){
+  if(!window._notificationsEnabled||!document.hidden) return;
+  if(!('Notification' in window)) return;
+  const botName=window._botName||'Hermes';
+  if(Notification.permission==='granted'){
+    new Notification(title||botName,{body:body});
+  }else if(Notification.permission!=='denied'){
+    Notification.requestPermission().then(p=>{
+      if(p==='granted') new Notification(title||botName,{body:body});
+    });
+  }
+}
+
 // ── Panel navigation (Chat / Tasks / Skills / Memory) ──
 

static/panels.js

@@ -1009,6 +1009,10 @@ async function loadSettingsPanel(){
     if(syncCb){syncCb.checked=!!settings.sync_to_insights;syncCb.addEventListener('change',_markSettingsDirty,{once:false});}
     const updateCb=$('settingsCheckUpdates');
     if(updateCb){updateCb.checked=settings.check_for_updates!==false;updateCb.addEventListener('change',_markSettingsDirty,{once:false});}
+    const soundCb=$('settingsSoundEnabled');
+    if(soundCb){soundCb.checked=!!settings.sound_enabled;soundCb.addEventListener('change',_markSettingsDirty,{once:false});}
+    const notifCb=$('settingsNotificationsEnabled');
+    if(notifCb){notifCb.checked=!!settings.notifications_enabled;notifCb.addEventListener('change',_markSettingsDirty,{once:false});}
     // Bot name
     const botNameField=$('settingsBotName');
     if(botNameField){botNameField.value=settings.bot_name||'Hermes';botNameField.addEventListener('input',_markSettingsDirty,{once:false});}
@@ -1045,6 +1049,8 @@ async function saveSettings(andClose){
   body.show_cli_sessions=showCliSessions;
   body.sync_to_insights=!!($('settingsSyncInsights')||{}).checked;
   body.check_for_updates=!!($('settingsCheckUpdates')||{}).checked;
+  body.sound_enabled=!!($('settingsSoundEnabled')||{}).checked;
+  body.notifications_enabled=!!($('settingsNotificationsEnabled')||{}).checked;
   const botName=(($('settingsBotName')||{}).value||'').trim();
   body.bot_name=botName||'Hermes';
   // Password: only act if the field has content; blank = leave auth unchanged
@@ -1065,6 +1071,8 @@ async function saveSettings(andClose){
     window._sendKey=sendKey||'enter';
     window._showTokenUsage=showTokenUsage;
     window._showCliSessions=showCliSessions;
+    window._soundEnabled=body.sound_enabled;
+    window._notificationsEnabled=body.notifications_enabled;
     window._botName=body.bot_name;
     if(typeof applyBotName==='function') applyBotName();
     _settingsDirty=false; _settingsThemeOnOpen=theme;