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-corn-2024-9609.md

@@ -0,0 +1,47 @@
+# Corn yield trial — Bruce Dutter (Flora, IN, 2024)
+
+- **Publisher:** ProHarvest Seeds (cross-vendor plot report)
+- **Crop:** Corn
+- **Year:** 2024
+- **Location:** Flora, IN · Carroll County
+- **Cooperator:** Bruce Dutter
+- **Company rep:** David Hopkins
+- **Planted:** 5/9/2024
+- **Harvested:** 10/17/2024
+- **Row width:** 30
+- **Population:** 35,000 seeds/acre
+- **Irrigation:** Non-Irrigated
+- **Source PDF:** https://proharvestseeds.com/wp-content/uploads/2024/11/Corn-Bruce-Dutter-Flora-IN-46929.pdf
+
+---
+
+## Results (head-to-head)
+
+| Rank | Brand | Hybrid/Variety | Trait | Yield/Ac | % H2O | Test Wt | +/- Ave |
+|---|---|---|---|---|---|---|---|
+| 1 | ProHarvest | 83P66 | VT2PRIB | 280.74 | 17.7 | 58.5 | 14.8 |
+| 2 | DEKALB | DKC110-41RIB | - | 280.63 | 14.5 | 59.7 | 14.7 |
+| 3 | Becks | 6374 | V2P | 280.47 | 16.5 | 60.4 | 14.5 |
+| 4 | Becks | 6184 | VT2PRIB | 277.98 | 15.8 | 60.5 | 12 |
+| 5 | Pioneer | P10811 | AM | 277.86 | 15.3 | 58.4 | 11.9 |
+| 6 | Becks | 6469 | V2P | 277.45 | 17.4 | 60.2 | 11.5 |
+| 7 | Pioneer | 13777 | PCE | 276.83 | 16.5 | 60.7 | 10.9 |
+| 8 | Becks | 6064 | AM | 273.02 | 15.7 | 60 | 7.1 |
+| 9 | Becks | 6485 | SX | 271.63 | 16.8 | 61 | 5.7 |
+| 10 | Becks | 5899 | SX | 271.16 | 14.9 | 59.7 | 5.2 |
+| 11 | DEKALB | DKC64-22RIB | - | 270.76 | 15.9 | 62.4 | 4.8 |
+| 12 | ProHarvest | 81P20 | PCE | 270.12 | 16.1 | 58.4 | 4.2 |
+| 13 | DEKALB | DKC111-35RIB | - | 269.25 | 15.5 | 62.3 | 3.3 |
+| 14 | Becks | 6585 | TCV2P | 266.82 | 16.9 | 61 | 0.9 |
+| 15 | Becks | 6241 | Q | 262.3 | 17 | 59 | -3.6 |
+| 16 | Pioneer | P1742 | Q | 262.16 | 16.4 | 58.8 | -3.8 |
+| 17 | ProHarvest | 77P19 | VT2PRIB | 261.13 | 14.1 | 59.8 | -4.8 |
+| 18 | ProHarvest | 85P58 | SSRIB | 260.64 | 15.9 | 63.2 | -5.3 |
+| 19 | Becks | 5794 | VT2PRIB | 259.31 | 14.7 | 59.4 | -6.6 |
+| 20 | Becks | 5530 | PCE | 259.01 | 14.7 | 58.2 | -6.9 |
+| 21 | DEKALB | DKC113-83RIB | - | 257.35 | 15.2 | 60.4 | -8.6 |
+| 22 | Becks | 5413 | Q | 254.84 | 14 | 59.4 | -11.1 |
+| 23 | Becks | 5824 | AM | 252.01 | 15.6 | 59.5 | -13.9 |
+| 24 | Becks | 6774 | VT2PRIB | 251.93 | 17.6 | 59.9 | -14 |
+| 25 | Becks | 6081 | AM | 248.33 | 15.3 | 59.2 | -17.6 |
+| 26 | Becks | 5929 | BZ | 240.52 | 15.4 | 58.2 | -25.4 |