Add PDF and DOCX export formats

[ysamlan]

HTML and gists for sharing is great. But we're looking for a few options that can work with non-engineering tools inside enterprise walls for use in "Compound Engineering" review sessions at my company.

• Add --format pdf and --format docx options
• Extract shared export helpers (extract_conversations, load_conversations, generate_single_page_html) into export_helpers.py
• New optional dependency groups: pip install claude-code-transcripts[pdf], [docx], or [export] for both

Testing

Besides the automated tests (29 new for PDF/DOCX):

Try PDF export

uv pip install -e '.[pdf]'
uv run claude-code-transcripts json tests/sample_session.json --format pdf

Try DOCX export

uv pip install -e '.[docx]'
uv run claude-code-transcripts json tests/sample_session.json --format docx