Support an OpenRouter provider (OpenAI-compatible gateway) so open models
like DeepSeek can run through the chat path, with stream_usage and retries
tuned for long agentic eval sessions. Add DeepSeek-V4-Flash pricing so
context_stats/cost telemetry populates, and LFS-track kb/generated/symbols.tsv.
Also harden .gitignore to ignore the top-level eval/ working dir wholesale,
preventing non-.jsonl student-text files (review_log_v1.md, review_batches/)
from slipping into git and onto the public prod Space.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
