Success stories: downloads and product sections become real plugins

- comparison report migrations/check_product_downloads.php (kept,
  read-only): download records vs. the delivered product workbooks -
  34 of 74 workbook products have a datasheet, the entire Datapath
  line has none in the pool (import came from vitec.com; queued for
  Joe), ~35 orphan datasheets belong to products without records;
  a vitec:link-product-downloads re-run added seven clean links
  (Artio x2, Diamond-H, the three TOUGH records, X-View)
- RTE resolution fixed at the root: ContentElementResolver and
  ContainerChildrenProcessor passed bodytext RAW into the payload, so
  t3:// links leaked unresolved; both now run RTE columns (bodytext,
  vitec_quote) through RteResolver::html()
- the imported "Download Success Story" RTE buttons carried the wrong
  link identifier (tx_vitec_download -> download, one-time migration
  fix_download_record_links.php) AND old-site uids - missing here or,
  worse, accidentally pointing at foreign PDFs. New
  vitec:convert-story-download-buttons replaces them with real
  vitec_downloadcard plugins: the download is resolved by STORY title
  (manual map for ISR / "Okada Manilla", exact-title fallback for
  suffixless PDFs like "Lord's Cricket Ground"); 29 converted, 4
  stories without a delivered PDF have their button hidden. New
  FlexForm layout "Success Story Download" (story_download) applied
  everywhere; the FE renders it as the previous centered button
- the ADIB "Featured Products" text section (the only one site-wide,
  verified by scan_story_headers.php) is now ONE vitec_productlist
  with hand-picked products via old-name aliases and the new FlexForm
  layout "Success Story Products" (story_products); the four text
  elements are deleted. vitec:convert-story-product-sections stays
  re-runnable for future imports
- the productlist envelope additionally carries "columns" (= number
  of products, capped at 4) so the story grid renders as many columns
  as it has products - additive key, available to every product list;
  and hand-picked lists now ship successStories as an empty array (the
  empty category selection used to aggregate stories over the WHOLE
  tree, leaking story cards into the section)
- the story downloadcards carry header "Downloads" (set on convert
  and backfilled): the front end builds the story anchor nav from
  element headers, so the section now appears there
- diagnosis scripts kept: check_download_record, check_story_elements,
  scan_story_headers; verified live on the ADIB payload (structured
  download object, productlist [5,18,6], texts 10 -> 5)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/vitec/Configuration/FlexForms/Downloadcard.xml

@@ -62,6 +62,10 @@
                                     <label>Neutral Layout</label>
                                     <value>neutral</value>
                                 </numIndex>
+                                <numIndex index="3">
+                                    <label>Success Story Download</label>
+                                    <value>story_download</value>
+                                </numIndex>
                             </items>
                         </config>
                     </settings.layout>