test: add comprehensive tests for Slack add-reaction tool

- Add route.test.ts for the add-reaction API route
  - Tests successful reaction addition
  - Tests authentication handling
  - Tests validation of required fields (access token, channel, timestamp, emoji)
  - Tests Slack API error handling (missing_scope, channel_not_found, message_not_found, invalid_name, already_reacted)
  - Tests network error handling
  - Tests various emoji names

- Add slack.test.ts for the Slack block configuration
  - Tests block configuration and tool access
  - Tests tools.config.tool function returns correct tool names
  - Tests tools.config.params correctly maps react operation params
  - Tests subBlocks configuration for react operation
  - Tests inputs configuration

Validates that the Slack add-reaction tool works correctly.

Co-authored-by: Emir Karabeg <emir-karabeg@users.noreply.github.com>

Author: cursoragent