Add Twitter tweet lookup tool

[Chel-Tbl]

Summary

• add a Twitter Get Tweet tool for looking up one tweet by ID
• fetch author expansion, created date, links, referenced tweet metadata, and public metrics
• expose the tool in the Twitter client/server toolkit registry and prompt guidance

Verification

• tsc --noEmit --pretty false
• targeted prettier --check for Twitter toolkit files
• git diff --check
• SKIP_ENV_VALIDATION=1 next build

Closes #242