feat: render article inline images as markdown

[jackwener]

Summary

• cherry-pick the inline article image rendering work from feat: render inline article images as markdown #32
• preserve existing atomic markdown block rendering from feat: preserve article atomic markdown blocks #37
• add mixed markdown + image regression coverage

Validation

• uv run pytest -q
• uv run mypy twitter_cli
• uv run ruff check twitter_cli/parser.py tests/test_client.py

Co-authored-by: alextuan1024 alextuan1024@gmail.com

[jackwener]

Thanks for the contribution here as well. We carried the inline article image work forward, preserved the recent atomic markdown block behavior, and kept co-author credit in the follow-up changes.