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>

server/src/routes/fights.ts

@@ -12,6 +12,13 @@ import { getPendingChallenge, submitHumanResponse } from '../engine/human-respon
 
 export const fightsRouter = new Hono()
 
+// Track spectator counts per fight
+const spectatorCounts = new Map<string, number>()
+
+export function getSpectatorCount(fightId: string): number {
+  return spectatorCounts.get(fightId) || 0
+}
+
 // List recent fights (with bot names)
 fightsRouter.get('/', async (c) => {
   const rows = await db.select()
@@ -322,10 +329,20 @@ fightsRouter.get('/:id/stream', (c) => {
   const fightId = c.req.param('id')
 
   return streamSSE(c, async (stream) => {
+    // Track spectator
+    spectatorCounts.set(fightId, (spectatorCounts.get(fightId) || 0) + 1)
+    const count = spectatorCounts.get(fightId)!
+
+    // Send initial spectator count
+    await stream.writeSSE({
+      event: 'spectator_count',
+      data: JSON.stringify({ count }),
+    })
+
     const cleanup = fightEvents.on(fightId, (event) => {
       stream.writeSSE({
         event: event.type,
-        data: JSON.stringify(event.data),
+        data: JSON.stringify({ ...event.data, spectators: spectatorCounts.get(fightId) || 0 }),
       })
     })
 
@@ -333,14 +350,17 @@ fightsRouter.get('/:id/stream', (c) => {
       if (event.fightId === fightId && event.type === 'fight_end') {
         stream.writeSSE({
           event: 'fight_end',
-          data: JSON.stringify(event.data),
+          data: JSON.stringify({ ...event.data, spectators: spectatorCounts.get(fightId) || 0 }),
         })
       }
     })
 
     try {
       while (true) {
-        await stream.writeSSE({ event: 'ping', data: '' })
+        await stream.writeSSE({
+          event: 'ping',
+          data: JSON.stringify({ spectators: spectatorCounts.get(fightId) || 0 }),
+        })
         await stream.sleep(5000)
         const fight = await db.select({ status: schema.fights.status })
           .from(schema.fights)
@@ -351,6 +371,13 @@ fightsRouter.get('/:id/stream', (c) => {
     } catch {
       // Client disconnected
     } finally {
+      // Decrement spectator count
+      const current = spectatorCounts.get(fightId) || 1
+      if (current <= 1) {
+        spectatorCounts.delete(fightId)
+      } else {
+        spectatorCounts.set(fightId, current - 1)
+      }
       cleanup()
       cleanupGlobal()
     }