remove: delete domain-specific use_cases cookbooks and docs (#647)

Removes all notebooks, data files, and exports under cookbook/use_cases/
(advanced_rag, biomedical, blockchain, capability_gap_defense, cybersecurity,
finance, intelligence, renewable_energy, supply_chain) and the corresponding
docs/use-cases.md page.

Cleans up all references in docs/cookbook.md, docs/docs.json,
docs/concepts.md, docs/modules.md, and docs/learning-more.md.

docs/docs.json

@@ -65,7 +65,6 @@
             "pages": [
               "concepts",
               "modules",
-              "use-cases",
               "glossary"
             ]
           },