Add ProHarvest Seeds: 119 varieties + 161 cross-vendor plot reports

ProHarvest Seeds (independent Corn Belt brand, proharvestseeds.com) exposes
a public, no-auth WordPress REST API — cleaner ingestion than the HTML-only
independents. Two new sources:

- `proharvest` (variety identity, 119 row-crop varieties: 70 corn / 47 soy /
  2 wheat). Enumerated via /wp/v2/seed (seed-type taxonomy), agronomics
  parsed from each /seed/<slug>/ detail page into structured
  characteristics_groups so the ratings actually embed. Mixed scale: disease
  1-9 numeric (9=best, no flip), agronomic/general qualitative, soil HR/R.

- `proharvest_plots` (trials, data_type=trial, 161 plots, 2024+2025). Per-
  cooperator harvest reports via the custom /wp-json/proharvest/v1/plots?y=
  endpoint + PDF table extraction. Many are cross-vendor head-to-head
  (ProHarvest/Apex vs Pioneer/DEKALB/Becks/Channel/Wyffels). Handles ruled
  tables, unruled tables (text fallback; soy drops the Test-Wt column → 4 vs
  5 numerics), and off-template third-party reports (sanity-gated to verbatim
  so junk rows never ship). Image-only PDFs skipped + counted.

- rag/chunk.py: route proharvest_plots through the shared cross-vendor plot
  renderer (structured) / verbatim body (raw_text fallback).
- sources.json + lessons.md (rating-scales, trial-data).
- README/CLAUDE.md corpus inventory brought current (it had drifted: bayer
  931 not 475; ebberts/lg/agrigold were unlisted). New totals: 1,645 variety
  + 6,787 trial records.

robots.txt permissive (only search + /dealer-* disallowed); no ToS
automation clause. CI rebuilds the index from the committed corpus.

corpus/proharvest_plots/phpr-soybeans-2024-9573.md

@@ -0,0 +1,36 @@
+# Soybean yield trial — Agrinetics Seed Service (Hinkley, IL, 2024)
+
+- **Publisher:** ProHarvest Seeds (cross-vendor plot report)
+- **Crop:** Soybean
+- **Year:** 2024
+- **Location:** Hinkley, IL · Dekalb County
+- **Cooperator:** Agrinetics Seed Service
+- **Company rep:** Jeff Horner
+- **Planted:** 4/22/2024
+- **Harvested:** 9/30/2024
+- **Previous crop:** Corn
+- **Row width:** 30"
+- **Population:** 140,000 seeds/acre
+- **Tillage:** Conventional
+- **Irrigation:** Non-Irrigated
+- **Fungicide:** Yes
+- **Source PDF:** https://proharvestseeds.com/wp-content/uploads/2024/11/Soy-Agrinetics-Hinckley-IL-60520.pdf
+
+---
+
+## Results (head-to-head)
+
+| Rank | Brand | Hybrid/Variety | Trait | Yield/Ac | % H2O | Test Wt | +/- Ave |
+|---|---|---|---|---|---|---|---|
+| 1 | NuTech | 25N05E | E3 | 90.88 | 11.7 | 56.6 | 6.1 |
+| 2 | NuTech | 24N05E | E3 | 89.34 | 11.6 | 56.5 | 4.5 |
+| 3 | NuTech | 27N07E | E3 | 87.31 | 12.0 | 55.9 | 2.5 |
+| 4 | ProHarvest | 25E35 | E3 | 86.78 | 11.7 | 55.6 | 2.0 |
+| 5 | NuTech | 28N03E | E3 | 85.97 | 11.7 | 57.2 | 1.2 |
+| 6 | NuTech | 29N05E | E3 | 85.24 | 11.6 | 56.6 | 0.4 |
+| 7 | NuTech | 30N06E | E3 | 84.66 | 12.2 | 56.4 | -0.1 |
+| 8 | NuTech | 26N08E | E3 | 84.33 | 11.7 | 56.3 | -0.5 |
+| 9 | Apex | AE2440 | E3 | 83.79 | 11.4 | 57.1 | -1.0 |
+| 10 | Apex | AE2740 | E3 | 83.51 | 11.7 | 57.0 | -1.3 |
+| 11 | Apex | AE2750 | E3 | 78.69 | 11.6 | 56.0 | -6.1 |
+| 12 | Apex | AE2940S | E3 | 77.25 | 12.3 | 55.2 | -7.6 |