[FEATURE] Generate values.schema.json from ate-setup's settings registry #3683

Produce each chart's values.schema.json from ate-setup's settings registry (cmd/ate-setup/internal/config/setting.go), so Helm rejects mistyped or unknown values with the same rules ate-setup applies.

Tracks "Generate the values schema" in the Helm Charts workstream of the Extensible Install Roadmap.

Required changes

• A generator from the settings registry to JSON Schema, covering the value paths in [FEATURE] Base Helm Values for Installers #3186, including sizing values ([FEATURE] Helm sizing values #3692).
• CI fails when the schema is stale.

Dependencies: #3186; #3682.

Enforcement: CI freshness check. helm lint rejects an unknown or mistyped value.

Parent Issue: #3170