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-2024-9533.md

@@ -0,0 +1,46 @@
+# Corn yield trial — Paul Young (Aledo, IL, 2024)
+
+- **Publisher:** ProHarvest Seeds (cross-vendor plot report)
+- **Crop:** Corn
+- **Year:** 2024
+- **Location:** Aledo, IL · Mercer County
+- **Cooperator:** Paul Young
+- **Company rep:** Ronn Dillavou
+- **Planted:** 4/23/2024
+- **Harvested:** 10/4/2024
+- **Previous crop:** Soybeans
+- **Row width:** 30"
+- **Population:** 35,000 seeds/acre
+- **Tillage:** Conventional
+- **Irrigation:** Non-Irrigated
+- **Fungicide:** Yes
+- **Source PDF:** https://proharvestseeds.com/wp-content/uploads/2024/11/Corn-Paul-Young-Aledo-IL-61231.pdf
+
+---
+
+## Results (head-to-head)
+
+| Rank | Brand | Hybrid/Variety | Trait | Yield/Ac | % H2O | Test Wt | +/- Ave |
+|---|---|---|---|---|---|---|---|
+| 1 | Brevant | B13C49 | PCE | 313.42 | 16.0 | 61.2 | 19.4 |
+| 2 | Brevant | B10Y21 | Vorceed | 312.83 | 14.0 | 60.2 | 18.8 |
+| 3 | LG | 63C54 | PCE | 309.1 | 15.6 | 60.9 | 15.1 |
+| 4 | Brevant | B11M47 | PCE | 307.9 | 15.6 | 62.3 | 13.9 |
+| 5 | Midwest | MW14-60 | TRE | 299.15 | 14.0 | 62.2 | 5.1 |
+| 6 | Brevant | B12H48 | PCE | 298.87 | 15.2 | 61.7 | 4.8 |
+| 7 | LG | 63C82 | DGVT2P | 298.27 | 14.6 | 61.9 | 4.2 |
+| 8 | Brevant | B13C49 | PCE | 298.27 | 15.5 | 62.3 | 4.2 |
+| 9 | Midwest | MW12-48 | DGVT2P | 298.12 | 15.5 | 61.1 | 4.1 |
+| 10 | Brevant | B16K30 | PCE | 297.27 | 14.8 | 61.4 | 3.2 |
+| 11 | ProHarvest | 78P23 | PCE | 296.88 | 13.6 | 63.1 | 2.9 |
+| 12 | Brevant | B10A20 | AM | 293.23 | 14.4 | 60.7 | -0.8 |
+| 13 | ProHarvest | 83P17 | PCE | 292.99 | 15.6 | 62.2 | -1.0 |
+| 14 | Brevant | B08R32 | AM | 291.2 | 13.7 | 59.7 | -2.8 |
+| 15 | Midwest | MW13-60 | PCE | 291.17 | 13.8 | 62.0 | -2.9 |
+| 16 | LG | 61C34 | SS | 290.54 | 14.3 | 59.3 | -3.5 |
+| 17 | Midwest | MW09-90 | PCE | 289.68 | 13.7 | 58.0 | -4.4 |
+| 18 | ProHarvest | 84P78 | TRE | 285.84 | 15.2 | 59.7 | -8.2 |
+| 19 | LG | 60C86 | 5222EZ | 282.49 | 14.9 | 60.5 | -11.5 |
+| 20 | LG | 63C32 | SSP | 281.56 | 15.0 | 62.1 | -12.5 |
+| 21 | Midwest | MW11-30 | TRE | 272.86 | 15.6 | 61.1 | -21.2 |
+| 22 | LG | 63C77 | SS | 267.05 | 14.5 | 62.4 | -27.0 |