fix: reject incomplete TweetDetail responses

[LuciusChen]

Summary

• require TweetDetail results to contain the requested focal tweet
• return a structured not_found error instead of ok: true with empty or reply-only data
• place the focal tweet before replies for stable CLI rendering
• add client and CLI regression coverage

This keeps downstream JSON consumers from treating an incomplete parse as a successful tweet read.

Fixes #53.

Validation

• 245 passed, 6 deselected
• ruff check .
• mypy twitter_cli