[codex] Align spring-platform with Variant language

[monadic]

Summary

• update spring-platform docs to use current ConfigHub language: Component, Variant, Base Variant, and Deployment Variant
• make dev/stage/prod read as Deployment Variants of the inventory-api Component
• keep ADT positioned as older teaching language rather than the main model
• point public Spring docs at the cub-gen Initiative GUI proof and add an AI smoke-test path for the gate card

Validation

• git diff --check
• ./scripts/verify.sh
• ./examples/springboot-paas/demo-initiative-gui.sh in confighub/cub-gen
• jq '.scenarios[] | {title, changed_field, route, decision, source_file, next_actions}' .tmp/springboot-initiative-gui/initiative-card.json in confighub/cub-gen