Mirrors the miner.py fix in this same branch. convo_miner.py had the
exact same 10 MB cap at line 58 that silently dropped long transcripts
via continue. Long Claude Code sessions, multi-year ChatGPT exports,
and lifetime Slack dumps all exceed 10 MB. Same silent-drop pattern,
different file.
Raised to 500 MB to match miner.py for consistency; downstream chunking
means source file size does not affect storage or embedding cost.
Tests: tests/test_convo_miner_size_cap.py (1 test)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
MSL