feat(skill): gsc_signal_delta helper + tests + code notes

custom-skills/35-seo-signal-validation/code/CLAUDE.md

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+# seo-signal-validation — code environment notes
+
+## Helper: scripts/gsc_signal_delta.py
+Deterministic L1/L4 GSC delta. Feed it two saved GSC query exports (recent,
+prior) as JSON or TSV (columns: query, clicks, impressions, position).
+
+```bash
+python3 scripts/gsc_signal_delta.py \
+  --recent recent.tsv --prior prior.tsv \
+  --recent-days 28 --prior-days 30 --claim-term "호텔"
+```
+Returns day-normalized site totals, top gainers/decliners, and a `verdict_hint`
+(heuristic only — the final verdict is the skill's job, after L2/L3).
+
+## Getting the exports
+`mcp__dda__gsc_fetch_performance` (property pinned per workspace, e.g. JHR
+`sc-domain:josunhotel.com`) → save the query-dimension rows to a file → run the
+script. GSC anonymizes ~43% of query clicks; the disclosed subset ≠ the whole.
+
+## Env / access
+- `GOOGLE_KG_API_KEY` for `mcp__ourseo__search_knowledge_graph` (L3).
+- GSC/GA4 only exist for first-party properties — third-party entities skip L1.
+- Never crawl/audit Marriott for JHR (sameAs only).