fix: resolve SkillsFlow skills display issue (fixes #12) (#23)

Three issues prevented skills from showing in the SkillsFlow panel:

1. Skills list was loaded only once (cached by flowsLoaded flag). After
   installing skills via the marketplace, returning to SkillsFlow would
   still show 'No skills installed' since the cached empty result was
   never refreshed. Fix: always reload skills when switching to the
   SkillsFlow tab.

2. When files_changed was broadcast after skill installation, it only
   refreshed the file tree but not the SkillsFlow skills panel. Fix:
   also refresh flow skills when files_changed fires while viewing
   SkillsFlow.

3. The gmail-email built-in skill was missing YAML frontmatter (name
   and description), so discoverSkills() silently skipped it. Fix: add
   proper frontmatter.

4. Error handling in loadFlowSkills() silently swallowed errors with an
   empty catch. Fix: log errors to console for debugging.

Co-authored-by: Kagura Chen <daniyuu19@sjtu.edu.cn>

Author: kagura-agent

skills/gmail-email/SKILL.md

@@ -1,3 +1,8 @@
+---
+name: gmail-email
+description: Send emails via Gmail SMTP using App Password authentication.
+---
+
 # Gmail Email Skill
 
 Send emails via Gmail SMTP.

src/voice/ui.html

@@ -1378,7 +1378,7 @@ <h3 style="margin:0;color:#8b949e;font-size:12px;text-transform:uppercase;letter
   if(v==='integrations'&&!integrationsLoaded){loadToolkits();integrationsLoaded=true;}
   if(v==='comms'&&!commsLoaded){loadTelegramStatus();loadWhatsAppStatus();loadPhoneWebhookUrl();commsLoaded=true;}
   if(v==='skills'&&!skillsLoaded){document.getElementById('skillsFrame').src='/api/skills-mp/proxy?path=/';skillsLoaded=true;}
-  if(v==='flows'&&!flowsLoaded){loadFlowSkills();loadSavedFlows();flowsLoaded=true;}
+  if(v==='flows'){loadFlowSkills();loadSavedFlows();flowsLoaded=true;}
   if(v==='scheduler'&&!schedulerLoaded){loadSchedules();schedulerLoaded=true;}
 }
 // Skills MP install handler
@@ -1427,7 +1427,7 @@ <h3 style="margin:0;color:#8b949e;font-size:12px;text-transform:uppercase;letter
     flowSkillsCache = d.skills || [];
     document.getElementById('flowSkillsSearch').value = '';
     renderFlowSkillsList(flowSkillsCache);
-  }).catch(function(){});
+  }).catch(function(err){ console.error('loadFlowSkills error:', err); });
   refreshFlowCommsStatus();
 }
 
@@ -1970,7 +1970,7 @@ <h3 style="margin:0;color:#8b949e;font-size:12px;text-transform:uppercase;letter
     thinkingEl.querySelector('.thinking-text').textContent+=m.text;
     conv.scrollTop=conv.scrollHeight;
     break;
-  case'files_changed':refreshFileTree();break;
+  case'files_changed':refreshFileTree();if(currentView==='flows'){loadFlowSkills();}break;
   case'error':appendConv('Error: '+escHtml(m.message),'system');break;
   case'schedule_start':
     var schEl=document.createElement('div');