feat: add Slack and Telegram adapters with adapter-owned routing

[Royal-lobster]

Summary

• Breaking change: Moves routing from global RoutingConfig into per-adapter constructor options (channels, tags, mentions). Removes Router class, webhookUrl/pings from FormattedAlert.
• New: SlackAdapter — Incoming Webhooks with Block Kit formatting, per-level channel routing, mention support, 429 retry
• New: TelegramAdapter — Bot API with HTML formatting, per-level forum topic routing, tag-to-topic mapping, @username mentions, 429 retry

Migration

Move routing.channels, routing.tags, and routing.pings into adapter constructors:

// Before
AlertLogger.init({
  adapters: [new DiscordAdapter({ webhookUrl: '...' })],
  routing: { channels: { critical: '...' }, pings: { critical: ['<@&role>'] } },
})

// After
AlertLogger.init({
  adapters: [
    new DiscordAdapter({
      webhookUrl: '...',
      channels: { critical: '...' },
      mentions: { critical: ['<@&role>'] },
    }),
  ],
})

Usage

const logger = AlertLogger.init({
  serviceName: 'my-api',
  adapters: [
    new SlackAdapter({
      webhookUrl: 'https://hooks.slack.com/services/...',
      channels: { critical: 'https://hooks.slack.com/services/.../critical' },
      mentions: { critical: ['<@U0123>'] },
    }),
    new TelegramAdapter({
      botToken: '123:ABC...',
      chatId: '-1001234567890',
      topics: { critical: 42, warning: 43, info: 44 },
      mentions: { critical: ['@oncall_dev'] },
    }),
  ],
})

Test plan

• 178 tests pass across 14 test files
• TypeScript compiles cleanly
• Package builds successfully (ESM + CJS + DTS)
• Manual test with real Slack webhook
• Manual test with real Telegram bot

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request implements Slack and Telegram adapters for the alert logger and refactors the routing system to be adapter-owned, removing the global Router and RoutingConfig. Core types like FormattedAlert were simplified by removing webhookUrl and pings to support this decentralized routing. Feedback focuses on aligning the new formatters with design specifications, such as ensuring the Slack context block is present in all alert phases and correcting emoji inconsistencies in the Telegram formatter. The reviewer also identified code duplication in the Telegram formatter and suggested formatting improvements for Slack fields and Telegram mentions. Additionally, several test files were flagged for violating project rules by explicitly importing Vitest globals.