ACCEPTANCE CRITERIA (11/11)

☑ 1. Script `scripts/fetch-commodity-prices.js` fetches 5 commodities from Alpha Vantage using config from `config/commodities.json`

☑ 2. Reads API key from `ALPHA_VANTAGE_KEY` environment variable -- never hardcoded, never logged

☑ 3. If API key is missing, prints clear setup instructions and exits with code 2 (FR-29)

☑ 4. Uses rate limiter at 5 req/min (0.083 req/sec) via `createLimiter(0.083)` to respect free tier

☑ 5. Handles Alpha Vantage rate limit response (JSON with `"Note"` key): wait 60s and retry once

☑ 6. Handles Alpha Vantage error response (JSON with `"Error Message"` key): log and skip commodity

☑ 7. Output `data/state/commodities-latest.json` with all commodity values, timestamps, and errors

☑ 8. Output appends to `data/timeseries/commodities.json` via `appendToSeries()`

☑ 9. Supports `--dry-run`, `--verbose`, `--help` flags

☑ 10. Each commodity fetched independently -- one failure does not block others

☑ 11. Exit code 0 on partial success, 1 on all failures, 2 on config error