feat: SSE live fight spectating with spectator count

Enable real-time fight spectating for all live fights (not just human
fights). Multiple spectators can watch simultaneously via SSE. Spectator
count is tracked per-fight and broadcast with every SSE event.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/game/tts-worker.ts

@@ -0,0 +1,51 @@
+// Web Worker for Kokoro TTS — runs ONNX neural network inference off the main thread.
+// This prevents the 1-5 second freezes that occur when generate() runs on the UI thread.
+
+let tts: any = null
+
+self.addEventListener('message', async (e: MessageEvent) => {
+  const msg = e.data
+
+  switch (msg.type) {
+    case 'init': {
+      try {
+        const { KokoroTTS } = await import('kokoro-js')
+        tts = await KokoroTTS.from_pretrained('onnx-community/Kokoro-82M-ONNX', {
+          dtype: 'q8',
+          device: null,
+          progress_callback: (p: any) => {
+            if (p.progress !== undefined) {
+              self.postMessage({ type: 'progress', progress: p.progress })
+            }
+          },
+        })
+        self.postMessage({ type: 'init-done' })
+      } catch (err) {
+        self.postMessage({ type: 'init-failed', error: String(err) })
+      }
+      break
+    }
+
+    case 'generate': {
+      if (!tts) {
+        self.postMessage({ type: 'generate-failed', id: msg.id, error: 'not initialized' })
+        break
+      }
+      try {
+        const result = await tts.generate(msg.text, {
+          voice: msg.voice,
+          speed: msg.speed,
+        })
+        // Copy to a standalone ArrayBuffer so we can transfer ownership (zero-copy to main thread)
+        const audio = new Float32Array(result.audio)
+        self.postMessage(
+          { type: 'generate-done', id: msg.id, audio, sampleRate: result.sampling_rate },
+          { transfer: [audio.buffer] },
+        )
+      } catch (err) {
+        self.postMessage({ type: 'generate-failed', id: msg.id, error: String(err) })
+      }
+      break
+    }
+  }
+})