Calibrator live mode: resolve listing URLs to product pages (not search pages)

From PR #142 (P5 Reality Calibrator) live verification.

resolveListingUrls (services/agents/src/calibrator/sample.ts) builds ${origin}/search?q=<name> — a brand DTC search-results page — plus an Amazon search URL. In live mode the Calibrator fetches that search page, Haiku-extracts facts from it, and writes them back into canonical subjects.facts.

Problems:

1. Search-results HTML is noisy → extraction quality / pollution risk on the reviewed catalog facts.
2. One listing per subject means the Reconciler never actually reconciles — the >10% numeric divergence hard-block can't trigger; method is always unanimous/most-recent.

Fix: resolve to real product-detail URLs per subject (a canonical product URL on the subject, a DTC product path, or human-fetch the product page), and/or gate live writeback behind review until ≥2 real product listings exist. Until then treat live writeback as untrusted — the deterministic calibrate <domain> --from-facts path is the reliable one for producing calibration_<q>.json.

Note: the committed --from-facts calibration_2026Q2.json (n=17) is unaffected; this concerns only the live scrape→writeback path.