fix(captures): Play As autoplay + default voice + orphan recovery

- Hand /generate ids to the global SSE watcher so playback fires on completion. The mutation onSuccess was checking audio_path on a queued row, which is always empty — autoplay never ran.
- Bind the Play As voice selection to capture_settings.default_playback_voice_id, kept in sync with the Settings → Captures and Settings → MCP pickers. Picking from the split-button dropdown writes back to settings.
- Extract AudioBars from HistoryTable into a shared component; use it for the Play As generating state in place of Loader2.
- Stop the active-state hover from flashing white text when the button is in its lighter accent/10 fill.
- Drop the gradient avatar swatches from the Settings → Captures voice dropdown.
- Backend: when the gen worker exits without writing a terminal status (e.g. SQLite lock racing the failed-status write inside its own exception handler), the cancel endpoint now flips the row to failed instead of 409-ing. Worker also force-fails on its way out as a belt-and-suspenders.

app/src/components/AudioBars.tsx

@@ -0,0 +1,39 @@
+import { motion } from 'framer-motion';
+
+import { cn } from '@/lib/utils/cn';
+
+export type AudioBarsMode = 'idle' | 'generating' | 'playing';
+
+interface AudioBarsProps {
+  mode: AudioBarsMode;
+  className?: string;
+  barClassName?: string;
+}
+
+export function AudioBars({ mode, className, barClassName }: AudioBarsProps) {
+  const activeColor = mode !== 'idle' ? 'bg-accent' : 'bg-muted-foreground/40';
+  return (
+    <div className={cn('flex items-center gap-[2px] h-5', className)}>
+      {[0, 1, 2, 3, 4].map((i) => (
+        <motion.div
+          key={`${mode}-${i}`}
+          className={cn('w-[3px] rounded-full', activeColor, barClassName)}
+          animate={
+            mode === 'generating'
+              ? { height: ['6px', '16px', '6px'] }
+              : mode === 'playing'
+                ? { height: ['8px', '14px', '4px', '12px', '8px'] }
+                : { height: '8px' }
+          }
+          transition={
+            mode === 'generating'
+              ? { duration: 0.6, repeat: Infinity, delay: i * 0.08, ease: 'easeInOut' }
+              : mode === 'playing'
+                ? { duration: 1.2, repeat: Infinity, delay: i * 0.15, ease: 'easeInOut' }
+                : { duration: 0.4, ease: 'easeOut' }
+          }
+        />
+      ))}
+    </div>
+  );
+}