Fix result display: audio player, error message, correct field names

- Use file_accomplished (not frozen+!error) to gate audio player
- Use errors field (was .error — wrong name, always falsy)
- Render <audio controls> instead of bare download link
- Add audiowidget.tmpl.stub for server-side customization

static/components/PaneCP.js

@@ -110,14 +110,22 @@ export const PaneCP = {
                 // Export error
                 exportError.value ? h('div', { class: 'se-error' }, exportError.value) : null,
 
-                // Status poller
+                // Status poller (while running)
                 store.synthesisStatus && !store.synthesisStatus.frozen
                     ? h(StatusPoller, { store }) : null,
 
-                // Result link
-                store.synthesisStatus?.frozen && !store.synthesisStatus?.error
-                    ? h('a', { href: '/sompyle/result.mp3', style: 'display:block;margin-top:0.5rem' },
-                        'Download result') : null,
+                // Synthesis error
+                store.synthesisStatus?.frozen && store.synthesisStatus?.errors
+                    ? h('div', { class: 'se-error', style: 'margin-top:0.5rem' },
+                        store.synthesisStatus.errors) : null,
+
+                // Audio result
+                store.synthesisStatus?.file_accomplished
+                    ? h('audio', {
+                        controls: true,
+                        src: '/sompyle/result.mp3',
+                        style: 'display:block;width:100%;margin-top:0.5rem',
+                      }) : null,
             ]);
         };
     },