- Add extract/extract_core/ workspace package with three modules:
- state.py: SQLite run tracking (open_state_db, start_run, end_run, get_last_cursor)
- http.py: niquests session factory + etag normalization helpers
- files.py: landing_path, content_hash, write_bytes_atomic (atomic gzip writes)
- State lives at {LANDING_DIR}/.state.sqlite — no extra env var needed
- SQLite chosen over DuckDB: state tracking is OLTP (row inserts/updates), not analytical
- Refactor all 4 extractors (psdonline, cftc_cot, coffee_prices, ice_stocks):
- Replace inline boilerplate with extract_core helpers
- Add start_run/end_run tracking to every extraction entry point
- extract_cot_year returns int (bytes_written) instead of bool
- Update tests: assert result == 0 (not `is False`) for the return type change
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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