chore: fix stale validator references in docs

- app/validate.py docstring: `python -m scripts.validate` -> `python -m app.validate`
  (no `scripts/` module exists; validator lives at app/validate.py, matching README + CI)
- .gitignore: drop stale note about non-existent `data/_staging/` directory

Refs #1

Author: Seungpyo1007

.gitignore

@@ -28,9 +28,6 @@ env/
 # Local tooling/editor config (kept out of the public repo)
 .claude/
 
-# Note: data/_staging/ (raw collected candidate pool) is intentionally tracked —
-# comprehensive data collection is a purpose of this repo.
-
 # Build-only: regenerated on every Pages deploy (site/scripts/build-*.mjs)
 site/public/v1/history.json
 site/public/v1/verification.json

app/validate.py

@@ -1,7 +1,7 @@
 """Validate seed JSON against the schema and conventions (§9.3, §15.3).
 
 Checks: required fields, slug convention (§14.1), value ranges/units (§14.3),
-and foreign-key integrity by slug. Run with ``python -m scripts.validate``;
+and foreign-key integrity by slug. Run with ``python -m app.validate``;
 exits non-zero on the first failure set (used by CI ``validate-data.yml``).
 """