Add 4 independent seed brands: Latham, Stine, 1st Choice, Burrus (+623 varieties)

Four independent regional brands across IA/IN/IL (variety-identity sources,
each parsed into structured characteristics_groups so ratings embed):

- latham (264: 155 corn + 109 soy) — Latham Hi-Tech Seeds, Alexander IA.
  WordPress REST enum (/wp-json/wp/v2/varieties) + /products/<slug>/ detail
  HTML. Scale 1-9 LOWER=better (reversed, like NK/AgriPro).
- stine (217: 58 corn + 159 soy) — Stine Seed, Adel IA (largest US
  independent). sitemap enum + /{crop}/traits/<slug>/<code>/ detail HTML.
  Corn 1-9 (9=best); soy qualitative.
- first_choice (78: 52 corn + 22 soy + 4 wheat) — 1st Choice Seeds,
  Rushville IN (employee-owned). Per-crop sitemap -> detail HTML. Scale
  0-10 higher=better. ~40 older corn pages thin at source; wheat
  identity-only.
- burrus (64: 38 corn + 26 soy) — Burrus Seed, Arenzville IL. Seedware
  JSON API. Scale 1-10 (10=best). Brands Burrus/Power Plus/DONMARIO.
  robots ai-train=no + named-bot blocks; operator opted in, scraper uses a
  non-blacklisted UA + honors Crawl-delay 10.

All 623 validated through rag.chunk.chunks_from_variety (0 errors; 6
identity-only pages from source gaps). No chunk.py change needed (identity
sources auto-route to chunks_from_variety).

Docs:
- sources.json: 4 entries + Hoegemeyer added to _excluded_sources. The
  Corteva ToU (shared across pioneer.com / hoegemeyer.com / therightseed.com
  / corteva.com + the Vylor spinoff) bans scrapers + competitive use, so the
  whole Corteva family is one excluded ToU domain.
- docs_mcp/lessons.md: rating-scales updated with all 4 directions +
  an explicit cross-vendor warning (Latham 1=best vs Stine/Burrus higher=best
  — never compare raw numbers without _scale_direction).
- README + CLAUDE corpus inventory: now 2,268 variety + 6,787 trial records.

CI rebuilds the index from the committed corpus.

corpus/stine/stine-47ff02.json

@@ -0,0 +1,129 @@
+{
+  "source": "stine",
+  "source_key": "stine-47ff02",
+  "vendor": "Stine Seed Company",
+  "brand": "Stine",
+  "product_name": "47FF02",
+  "product_id": "47FF02",
+  "crop": "soybeans",
+  "release_year": null,
+  "relative_maturity": null,
+  "maturity_group": 4.7,
+  "wheat_class": null,
+  "trait_stack": [
+    "XtendFlex"
+  ],
+  "trait_descriptions": [],
+  "positioning_statement": null,
+  "strengths": [],
+  "characteristics_groups": [
+    {
+      "label": "AGRONOMIC CHARACTERISTICS",
+      "items": [
+        {
+          "characteristic": "Maturity (RM)",
+          "value": "47"
+        },
+        {
+          "characteristic": "Emergence",
+          "value": "Very Good"
+        },
+        {
+          "characteristic": "Standability",
+          "value": "Very Good"
+        }
+      ]
+    },
+    {
+      "label": "DISEASE RATINGS",
+      "items": [
+        {
+          "characteristic": "Phytophthora Root Rot",
+          "value": "Very Good"
+        },
+        {
+          "characteristic": "RPS Gene",
+          "value": "S"
+        },
+        {
+          "characteristic": "Iron Deficiency Chlorosis",
+          "value": "Average"
+        },
+        {
+          "characteristic": "Brown Stem Rot",
+          "value": "Resistant"
+        },
+        {
+          "characteristic": "Sudden Death Syndrome",
+          "value": "Average"
+        },
+        {
+          "characteristic": "Soybean Cyst Nematode",
+          "value": "Resistant"
+        },
+        {
+          "characteristic": "Frogeye Leafspot",
+          "value": "Susceptible"
+        },
+        {
+          "characteristic": "Stem Canker",
+          "value": "Resistant"
+        },
+        {
+          "characteristic": "Root Knot Nematode",
+          "value": "Susceptible"
+        }
+      ]
+    },
+    {
+      "label": "PLANT DESCRIPTION",
+      "items": [
+        {
+          "characteristic": "Height",
+          "value": "Medium"
+        },
+        {
+          "characteristic": "Flower",
+          "value": "Purple"
+        },
+        {
+          "characteristic": "Pubescence",
+          "value": "Tawny"
+        },
+        {
+          "characteristic": "Hilum",
+          "value": "Black"
+        },
+        {
+          "characteristic": "Chloride",
+          "value": "Excluder"
+        }
+      ]
+    },
+    {
+      "label": "HERBICIDE TOLERANCE",
+      "items": [
+        {
+          "characteristic": "Sulfonylurea Tolerance",
+          "value": "-"
+        }
+      ]
+    }
+  ],
+  "_scale_direction": "corn agronomic+disease 1-9 numeric, 9=Excellent/best/most-tolerant, 8=Very Good, 7=Good, 6=Average, 5=Below Average (higher=better, same direction as Bayer/NK; blank/'-'=not rated); soybeans qualitative (Excellent/Very Good/Good for vigor; Resistant/Strong/Good/Susceptible for disease, Resistant/Strong=best); SCN row gives source (e.g. Peking) and RPS Gene gives the gene, not a rating; plant/soil/herbicide rows qualitative (Tall, Highly Recommended/Recommended, Yes/No)",
+  "regional_recommendations": [
+    {
+      "product_list_name": "Stine dealer network (Corn Belt — IA/IL/IN/MN/NE/MO etc.)",
+      "agronomist": null,
+      "agronomist_email": null,
+      "variant_id": null
+    }
+  ],
+  "image_url": null,
+  "source_urls": [
+    "https://www.stineseed.com/soybeans/traits/xtendflex-soybeans/47ff02/"
+  ],
+  "sitemap_last_modified": "2025-11-06T19:37:24+00:00",
+  "fetched_at": "2026-06-05T01:49:57.356637+00:00",
+  "scraper_version": "0.1.0"
+}