fix: harden bot lifecycle, validate HTTP inputs, make YouTube truly optional

Major bug fixes and corner-case hardening across the backend, plus a
comprehensive feature test suite. All 94 unit tests + 51 integration
tests pass against a local TS3 server.

Lifecycle & state consistency
-----------------------------
- Bug A: startBot() now wraps connect() in a 15s deadline. A hung TS
  handshake no longer blocks the /start HTTP call forever; the failing
  instance is torn down and the caller gets a clean 500.
- Bug B: executeCommand rejects audio-dispatching commands (play, add,
  next, skip, prev, playlist, album, fm) when the bot is disconnected.
  Config-only commands (vol, mode, clear, stop, queue, now, lyrics)
  still work so the UI stays usable while offline.
- Bug C: the tsClient 'disconnected' handler always clears player state
  now, even when connect() never completed. A separate disconnectEmitted
  flag guards duplicate external event emission. Previously an orphaned
  connect attempt that idle-timed-out would leave playing=true forever.
- resolveAndPlay re-checks this.connected AFTER the URL-resolve await so
  a stop() during the network call can't spawn ffmpeg on a disconnected
  bot.
- connect() throws if disconnect() fired during the handshake await,
  preventing a concurrent stop from being overwritten by a late connected
  flag flip.
- startBot always disconnects the outgoing BotInstance before creating
  a replacement, covering the mid-handshake case where isConnected()
  still returned false but the library client was live.
- startBot now reuses the stored identity so server groups granted to
  the bot survive restarts (was regenerating a fresh UID each time).

WebSocket reliability
---------------------
- BotManager extends EventEmitter and emits 'botInstance' whenever a
  new instance is created. websocket.ts listens and re-attaches its
  stateChange / connected / disconnected listeners immediately, fixing
  the bug where player-bar UI never updated until manual refresh.
- attachedBots map now stores the BotInstance reference and detaches
  stale listeners when the instance is replaced. Safety-net interval
  (5s) also reconciles to catch anything missed.
- removeBot emits 'botInstanceRemoved' -> WS broadcasts a new
  {type:"botRemoved", botId} message. Client drops the bot from its
  local store instead of showing it as permanently offline.

HTTP input validation
---------------------
- /volume rejects non-number, NaN, Infinity, and out-of-range values
  with a proper 400 instead of a 200 OK wrapping a usage-text string.
- /mode rejects anything not in {seq, loop, random, rloop} with 400.
- /seek rejects NaN / Infinity / negative (previously NaN slipped
  through typeof==="number" and poisoned seekOffset).
- /play-at validates index < queue.size() BEFORE stopping current
  playback (was silently killing the current song on invalid input).
- /play, /add, /playlist, /play-by-id, /add-by-id, /play-playlist
  all honour platform=youtube now (previously fell through to netease
  and silently played the wrong platform).

YouTube made truly optional
---------------------------
- Lazy checkYtDlpAvailable() runs `yt-dlp --version` once, caches only
  positive results so users can install yt-dlp mid-run and have it
  picked up without a restart.
- getAuthStatus() returns loggedIn=false with nickname
  "YouTube (yt-dlp not installed)" when the binary is missing. UI can
  grey out YouTube instead of silently returning empty searches.
- findYtDlp() picks .exe on win32 and bare binary elsewhere.
- /auth/status?platform=youtube now routes to the YouTube provider
  instead of falling through to NetEase and leaking the NetEase
  user's nickname + avatar.
- /auth/cookie rejects platform=youtube with 400 instead of clobbering
  the NetEase cookie entry.
- README documents yt-dlp install paths (bin/ local vs PATH) and adds
  a dedicated "Optional: YouTube source" section.

Bot Selector UI
---------------
- New power button in each row of the dropdown with play-state-aware
  styling: disabled + wait-cursor during API call, green highlight when
  connected, greys out when the bot is offline.
- Dropdown always visible when >=1 bot exists, bigger font + padding.

Queue correctness
-----------------
- PlayQueue.remove(current) now decrements currentIndex so next() in
  sequential mode advances to the shifted song. Previously removing
  the currently-playing track silently skipped the next track because
  current() falsely reported it as active and next() then incremented
  past it.

Vote-skip hardening
-------------------
- cmdVote: needed threshold is Math.max(1, ceil(users/2)) so a single
  voter in an empty channel can't unanimously pass a vote with
  needed=0.
- resolveAndPlay clears voteSkipUsers on every new track load so votes
  can't leak across songs via cmdPlay/cmdPlaylist/cmdAlbum/cmdFm paths.

cmdAdd parity
-------------
- cmdAdd auto-plays the newly-added song if the player was idle,
  matching /api/player/:id/add-by-id behaviour. Previously add'ing to
  an empty queue on a connected+idle bot silently enqueued without
  starting playback.

Test suite
----------
- scripts/test_full_feature.py — 51 tests across 10 groups exercising
  every HTTP endpoint, WebSocket broadcasts, all music providers, bot
  lifecycle, disconnected-state corners, seek validation, input
  validation, and the main race conditions. Captures and restores the
  target bot's initial state. Resilient to TS3 anti-flood via retry
  with exponential backoff. Runs against a real local TS3 server.
- scripts/test_rapid_cycle.py — Bugs A/B/C regressions
- scripts/test_corner_cases.py — disconnect-during-connect race, config
  commands while disconnected, etc.
- scripts/test_more_corners.py — resolveAndPlay race, seek NaN
- scripts/test_power_button.py — E2E for the new power button
- scripts/test_bot_remove.py — E2E for WS botRemoved broadcast
- scripts/test_playbar.py — player bar auto-show regression (updated
  to restore bot state on exit)
- scripts/test_multibot.py — two-bot concurrent playback monitor
- src/audio/queue.test.ts — 4 new vitest cases for remove() edge cases

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web/src/components/Navbar.vue

@@ -36,6 +36,15 @@
               <span v-else-if="bot.connected" class="bot-idle-badge">空闲</span>
               <span v-else class="bot-offline-badge">离线</span>
             </button>
+            <button
+              class="bot-power-btn"
+              :class="{ online: bot.connected }"
+              :title="bot.connected ? `停止 ${bot.name}` : `启动 ${bot.name}`"
+              :disabled="togglingBots[bot.id]"
+              @click.stop="togglePower(bot)"
+            >
+              <Icon :icon="bot.connected ? 'mdi:power' : 'mdi:power-off'" />
+            </button>
             <button class="bot-link-btn" :title="`复制 ${bot.name} 的专属链接`" @click.stop="copyBotLink(bot.id)">
               <Icon icon="mdi:link-variant" />
             </button>
@@ -61,6 +70,7 @@ const store = usePlayerStore();
 const activeBot = computed(() => store.activeBot);
 const dropdownOpen = ref(false);
 const selectorRef = ref<HTMLElement | null>(null);
+const togglingBots = ref<Record<string, boolean>>({});
 
 function selectBot(id: string) {
   store.setActiveBotId(id);
@@ -74,6 +84,22 @@ function copyBotLink(id: string) {
   });
 }
 
+async function togglePower(bot: { id: string; connected: boolean; name: string }) {
+  if (togglingBots.value[bot.id]) return;
+  togglingBots.value[bot.id] = true;
+  try {
+    if (bot.connected) {
+      await store.stopBotInstance(bot.id);
+    } else {
+      await store.startBotInstance(bot.id);
+    }
+  } catch (err) {
+    console.error(`Failed to toggle bot ${bot.name}`, err);
+  } finally {
+    togglingBots.value[bot.id] = false;
+  }
+}
+
 function onClickOutside(e: MouseEvent) {
   if (selectorRef.value && !selectorRef.value.contains(e.target as Node)) {
     dropdownOpen.value = false;
@@ -274,6 +300,32 @@ onUnmounted(() => {
   }
 }
 
+.bot-power-btn {
+  flex-shrink: 0;
+  padding: 6px 8px;
+  border-radius: var(--radius-sm);
+  font-size: 16px;
+  opacity: 0.5;
+  color: var(--text-tertiary);
+  transition: opacity var(--transition-fast), background var(--transition-fast), color var(--transition-fast);
+  cursor: pointer;
+
+  &:hover:not(:disabled) {
+    opacity: 1;
+    background: var(--hover-bg);
+  }
+
+  &:disabled {
+    opacity: 0.25;
+    cursor: wait;
+  }
+
+  &.online {
+    color: #22c55e;
+    opacity: 0.9;
+  }
+}
+
 .bot-playing-badge,
 .bot-paused-badge,
 .bot-idle-badge,

web/src/composables/useWebSocket.ts

@@ -56,6 +56,13 @@ export function useWebSocket() {
             }
           }
           break;
+        case 'botRemoved':
+          // Bot was deleted from the server — drop from local state entirely
+          store.removeBotStatus(data.botId);
+          if (store.activeBotId === data.botId) {
+            store.activeBotId = store.bots[0]?.id ?? null;
+          }
+          break;
       }
     };
 

web/src/stores/player.ts

@@ -168,6 +168,14 @@ export const usePlayerStore = defineStore('player', {
       if (saved) this.theme = saved;
     },
 
+    async startBotInstance(id: string) {
+      await axios.post(`/api/bot/${id}/start`);
+    },
+
+    async stopBotInstance(id: string) {
+      await axios.post(`/api/bot/${id}/stop`);
+    },
+
     async fetchBots() {
       const res = await axios.get('/api/bot');
       this.bots = res.data.bots;