fix: per-bot queue fixes — outer loop transient retry, getFileInfo logging, test file, safety net comment, empty-bot guard

- Add MAX_OUTER_RETRIES constant and transientAttempts counter for outer-loop retry
- Restore getFileInfo transient retry logging with bot identity and fileId
- Create test/bot-pool.test.ts with 4 tests for core BotPool behavior
- Add empty-bots guard in selectBot() returning null
- Add safety net comment and improved logging for outer 429 catch

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

test/bot-pool.test.ts

@@ -0,0 +1,131 @@
+import { afterEach, beforeEach, describe, expect, it, mock } from 'bun:test';
+
+process.env.BOT_TOKEN = 'bot1:token';
+process.env.ADDITIONAL_BOT_TOKENS = 'bot2:token,bot3:token';
+process.env.STORAGE_CHANNEL_ID = '-1001234567890';
+process.env.BASE_URL = 'https://example.com';
+process.env.DATABASE_URL = 'sqlite://test.db';
+process.env.PORT = '3000';
+
+// Track mock queue instances for per-bot assertions
+const queueInstances: Array<{
+  concurrency: number;
+  add: ReturnType<typeof mock>;
+  pending: number;
+  size: number;
+}> = [];
+
+// Mock PQueue so we can verify concurrency
+const mockAdd = mock(function addFn(this: any, fn: () => Promise<any>) {
+  return Promise.resolve().then(() => fn());
+});
+
+mock.module('p-queue', () => {
+  return {
+    default: mock(function MockQueue(this: any, opts?: { concurrency?: number }) {
+      const instance = {
+        concurrency: opts?.concurrency ?? 1,
+        add: mockAdd,
+        pending: 0,
+        size: 0,
+      };
+      queueInstances.push(instance);
+      return instance;
+    }),
+  };
+});
+
+// Mock Telegraf — use a class so `new Telegraf(token)` works correctly
+const mockTelegramInstances: Record<
+  string,
+  {
+    token: string;
+    sendDocument: ReturnType<typeof mock>;
+    sendPhoto: ReturnType<typeof mock>;
+    getFile: ReturnType<typeof mock>;
+  }
+> = {};
+
+class MockTelegraf {
+  token: string;
+  telegram: {
+    token: string;
+    sendDocument: ReturnType<typeof mock>;
+    sendPhoto: ReturnType<typeof mock>;
+    getFile: ReturnType<typeof mock>;
+  };
+
+  constructor(token: string) {
+    this.token = token;
+    this.telegram = {
+      token,
+      sendDocument: mock(() =>
+        Promise.resolve({
+          message_id: 1,
+          document: { file_id: `file_${token}`, file_unique_id: `uniq_${token}` },
+        }),
+      ),
+      sendPhoto: mock(() =>
+        Promise.resolve({
+          message_id: 1,
+          photo: [{ file_id: `photo_${token}`, file_unique_id: `photo_uniq_${token}` }],
+        }),
+      ),
+      getFile: mock(() =>
+        Promise.resolve({ file_size: 100, mime_type: 'text/plain', file_path: 'path' }),
+      ),
+    };
+    mockTelegramInstances[token] = this.telegram;
+  }
+}
+
+mock.module('telegraf', () => ({
+  Telegraf: MockTelegraf,
+}));
+
+describe('BotPool', () => {
+  let BotPool: typeof import('../src/infrastructure/telegram/bot-pool').BotPool;
+  let botPool: import('../src/infrastructure/telegram/bot-pool').BotPool;
+
+  beforeEach(async () => {
+    mockAdd.mockClear();
+    queueInstances.length = 0;
+    for (const token of Object.keys(mockTelegramInstances)) {
+      const tg = mockTelegramInstances[token];
+      if (tg) {
+        tg.sendDocument?.mockClear();
+        tg.getFile?.mockClear();
+      }
+    }
+    const mod = await import('../src/infrastructure/telegram/bot-pool');
+    BotPool = mod.BotPool;
+    botPool = new BotPool();
+  });
+
+  afterEach(() => {
+    // No module cache cleanup needed — Bun handles import caching correctly
+  });
+
+  it('should have correct bot count', () => {
+    expect(botPool.size).toBe(3);
+  });
+
+  it('should have correct effective concurrency', () => {
+    // 3 bots * 1 concurrency per bot
+    expect(botPool.getEffectiveConcurrency()).toBe(3);
+  });
+
+  it('should forward files through the queue', async () => {
+    const result = await botPool.forwardToStorage(Buffer.from('test data'), 'test.txt', 'document');
+    expect(result.telegramFileId).toBeDefined();
+    expect(result.storageMessageId).toBeGreaterThan(0);
+  });
+
+  it('should use per-bot queues with concurrency=1', () => {
+    // Each bot gets its own PQueue instance with concurrency=1
+    expect(queueInstances.length).toBe(3);
+    for (const qi of queueInstances) {
+      expect(qi.concurrency).toBe(1);
+    }
+  });
+});