* fix: prevent KeyError crash and context exhaustion in TOC processing
- Use .get() with safe defaults for all LLM response dict accesses
- Optimize extract_toc_content retry loop to grow chat_history
incrementally instead of rebuilding with full accumulated response
- Optimize toc_transformer retry loop to use chat_history instead of
re-embedding the entire raw TOC and incomplete JSON in each prompt
- Return best-effort results on max retries instead of raising
- Add 14 mock-based tests covering all fix scenarios
Closes#163
* fix: address review feedback on retry behavior and None guard
- Restore explicit Exception on max retries instead of silent warning
- Move truncation logic before the retry loop so it only runs once
on the initial incomplete response, not on every iteration
- Add explicit None guard for physical_index before passing to
convert_physical_index_to_int to prevent potential TypeError
- Update test to expect Exception on max retries
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Co-authored-by: Your Name <you@example.com>
