bayer_seeds: add Channel + DEKALB silage/sorghum/canola + Deltapine cotton

User flagged that Channel is expanding into their area — re-walked
the cropscience.bayer.us sitemap and found 8 additional brand×crop
paths beyond the original DEKALB/Asgrow/WestBred triple. Patches
the scraper to walk all of them; total Bayer varieties roughly
doubles from 475 to 931 and the corpus picks up first-ever
coverage in sorghum (36), cotton (30), canola (6), and silage as a
distinct crop (was conflated with corn before).

Net new varieties: 456
  Channel    corn=181  soy=67   silage=54  sorghum=18    (320)
  DEKALB     silage=82 sorghum=18  canola=6              (106)
  Deltapine  cotton=30                                    (30)

scrape/sources/bayer_seeds.py
- Replace `BRANDS` (brand → 1 path) and `CROP_SUFFIX` (brand → 1
  suffix) with a flatter `BRAND_PATHS` list of (brand, url_path,
  crop, is_primary_for_brand) entries. Channel and DEKALB are now
  multi-crop brands; the same scraper walks every brand×crop pair.
- source_key derivation: for a brand's PRIMARY crop, strip the
  trailing `-<crop>` suffix (matches the existing deployed source
  keys for DEKALB corn / Asgrow soy / WestBred wheat). For
  SECONDARY crops, KEEP the suffix so DEKALB-the-same-SKU sold as
  both grain corn and silage gets two distinct source_keys
  (collision-safe and unambiguous for `lookup_variety`).
- New `--crop` CLI filter for incremental backfills.
- Log line shows brand + crop alongside source_key for visibility.

rag/chunk.py
- Channel + Deltapine pages use slightly different characteristics
  group labels (DISEASE not DISEASE RATINGS, AGRONOMIC
  CHARACTERISTICS not GROWTH/HARVEST, plus MATURITY / ADAPTATION /
  HERBICIDES / OTHER). Fold them into the DISEASE / AGRONOMIC /
  MANAGEMENT label sets so the chunker buckets them correctly
  into the standard sections.

Smoke-tested cross-brand × cross-crop queries against the rebuilt
index (5,529 chunks total) — all 6 sample queries surface the
right brand+crop at top-3:
  Channel corn 110 RM       → 210-25TRE BRAND
  Channel soy 2.5 MG IA     → 2622RXF BRAND
  Deltapine cotton XF       → DP 1820 B3XF BRAND
  Sorghum dryland Kansas    → 6B95 BRAND (Channel)
  Silage corn WI dairy      → DKC64-44RIB BRAND BLEND (silage variant)
  Canola Northern Plains    → DK401TL BRAND

Watchtower will pull the new image on the next push; deploy is
unchanged otherwise.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

corpus/bayer_seeds/channel-3124rxf-soybeans.md

@@ -0,0 +1,86 @@
+# 3124RXF BRAND
+
+- **Vendor:** Bayer
+- **Brand:** Channel
+- **Crop:** Soybeans
+- **Maturity group:** 3.1
+- **Traits:** XF (XtendFlex)
+- **Release year:** 2024
+- **Source:** https://www.cropscience.bayer.us/soybeans/channel/channel-3124rxf-soybeans
+- **Rating scale (Bayer):** 1-9 (9 = best)
+
+---
+## Positioning
+
+3.1 MG XtendFlex® soybean that brings good disease tolerance to the early-3 maturity group
+
+## Strengths & management
+
+- Very good tolerances to Sclerotinia White Mold and Sudden Death Syndrome
+- Very good standability in a medium-bushy plant
+
+## Adaptation
+
+| Characteristic | Value |
+|---|---|
+| NARROW ROW | 2 |
+
+## Agronomic Characteristics
+
+| Characteristic | Value |
+|---|---|
+| EMERGENCE | 2 |
+| FLOWER COLOR | P |
+| GROWTH HABIT | Indeterminate |
+| HILUM COLOR | Ib |
+| NO-TILL ADAPTABILITY | 1 |
+| OIL CONTENT @ 13% MOISTURE | 21.56 |
+| PLANT HEIGHT | M |
+| POD COLOR | Br |
+| PROTEIN CONTENT @ 13% MOISTURE | 39.48 |
+| PUBESCENCE COLOR | Gr |
+| PLANT TYPE | Medium Bushy |
+| RELATIVE MATURITY | 3.1 |
+| STANDABILITY | 3 |
+
+## Disease Tolerance
+
+| Characteristic | Value |
+|---|---|
+| BROWN STEM ROT | 3 |
+| IRON DEFICIENCY CHLOROSIS | 6 |
+| PRR GENE | Rps1c |
+| PRR FIELD TOLERANCE | 5 |
+| SOUTHERN STEM CANKER | 3 |
+| SOYBEAN CYST NEMATODE | R3 |
+| SUDDEN DEATH SYNDROME | 4 |
+| WHITE MOLD | 4 |
+
+## Other
+
+| Characteristic | Value |
+|---|---|
+| HERBICIDE TOLERANT TRAIT | XF |
+| MATURITY GROUP | 3 |
+| TRAIT | XF |
+| VARIETY CODE | 1098110 |
+
+## Regional seed-guide listings
+
+- **2024-2025 South Central NE Soybean Products** — agronomist: Tyler Vreugdenhil
+- **Lauren Botine's Product List 2025** — agronomist: Lauren Botine
+- **2025 SW Indiana Product Characteristics and Management** — agronomist: Brian Denning
+- **South Eastern Indiana Channel Positioning 2025** — agronomist: Cody Hornaday
+- **SW Ohio Corn, Soybeans, and Silage MY25** — agronomist: Sam Park
+- **Ohio Corn, Soybeans, and Silage MY25** — agronomist: Mitchell Greve
+- **2025 Northern Indiana Soybean Product List** — agronomist: Jeff Lakin
+- **2025 NE Nebraska** — agronomist: Pat Koenig
+- **Central & Western VA** — agronomist: Jarette Hurry
+- **2025 KY Channel Corn & Soy** — agronomist: Luke Watson
+- **Southeastern Illinois Product List** — agronomist: Lindsey McKinzie
+- **East Central Illinois** — agronomist: Ryan Becker
+- **Southwest Iowa** — agronomist: Lance Porter
+- **2025 Northern Indiana Soybean Product List** — agronomist: Amanda Schwartz
+- **2025 East Central NE Soybean Products** — agronomist: Andrew Swanson
+- **Soybean SW/SC Kansas 2025** — agronomist: Mark Bartel
+- **2025 West Central Indiana Soybean Product List** — agronomist: Blake Russel