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>

src/bot/manager.ts

@@ -12,6 +12,42 @@ import type { Logger } from "../logger.js";
 
 import type { ServerProtocol } from "../ts-protocol/client.js";
 
+/**
+ * Run bot.connect() with a hard deadline. If the handshake hangs (e.g. the
+ * server silently drops the connection after initivexpand2), we tear the
+ * instance down instead of waiting for the library's 60s idle timeout, so
+ * the HTTP /start call returns promptly and the UI doesn't lock up.
+ */
+async function connectWithTimeout(
+  bot: BotInstance,
+  ms: number,
+  logger: Logger
+): Promise<void> {
+  let timer: ReturnType<typeof setTimeout> | undefined;
+  const timeout = new Promise<never>((_, reject) => {
+    timer = setTimeout(
+      () => reject(new Error(`connect timeout after ${ms}ms`)),
+      ms
+    );
+  });
+  try {
+    await Promise.race([bot.connect(), timeout]);
+  } catch (err) {
+    logger.warn(
+      { err, botId: bot.id },
+      "Connect failed or timed out — tearing down instance"
+    );
+    try {
+      bot.disconnect();
+    } catch {
+      // ignore teardown errors
+    }
+    throw err;
+  } finally {
+    if (timer) clearTimeout(timer);
+  }
+}
+
 export interface CreateBotParams {
   name: string;
   serverAddress: string;
@@ -111,6 +147,7 @@ export class BotManager extends EventEmitter {
       this.bots.delete(id);
     }
     this.database.deleteBotInstance(id);
+    this.emit("botInstanceRemoved", id);
     this.logger.info({ botId: id }, "Bot instance removed");
   }
 
@@ -155,6 +192,18 @@ export class BotManager extends EventEmitter {
     const oldBot = this.bots.get(id);
     if (!oldBot) throw new Error(`Bot ${id} not found`);
 
+    // Always tear down the outgoing instance before creating a replacement.
+    // Covers three cases:
+    //   1. oldBot is fully connected (manual restart)
+    //   2. oldBot is mid-handshake from a prior rapid start (isConnected()
+    //      still returns false but the library client is live and will leak
+    //      a TS session if we abandon it)
+    //   3. oldBot was just created by createBot but never connected — the
+    //      disconnect call is a cheap no-op here.
+    // Calling disconnect() is idempotent (disconnectEmitted guards event
+    // emission), so this is safe in all states.
+    oldBot.disconnect();
+
     // Reload config from database so updated settings (channel, nickname, etc.) take effect
     const saved = this.database.getBotInstances().find((i) => i.id === id);
     if (saved) {
@@ -167,6 +216,10 @@ export class BotManager extends EventEmitter {
           port: saved.serverPort,
           queryPort: proto === "ts6" ? 10080 : 10011,
           nickname: saved.nickname,
+          // Reuse the stored identity so server groups assigned to this bot
+          // survive restarts — without this the TS server sees a new UID
+          // each connect and strips all previously granted groups.
+          identity: saved.identity || undefined,
           defaultChannel: saved.defaultChannel || undefined,
           channelPassword: saved.channelPassword || undefined,
           serverPassword: saved.serverPassword || undefined,
@@ -183,12 +236,12 @@ export class BotManager extends EventEmitter {
       });
       this.bots.set(id, bot);
       this.emit("botInstance", bot);
-      await bot.connect();
+      await connectWithTimeout(bot, 15_000, this.logger);
       // Mark as autoStart so it reconnects on Docker restart, and persist identity
       this.database.saveBotInstance({ ...saved, autoStart: true });
       this.persistBotIdentity(saved, bot);
     } else {
-      await oldBot.connect();
+      await connectWithTimeout(oldBot, 15_000, this.logger);
     }
   }