Why: Generative UI U5 left the B-class action allowlist empty; owner
authorized first entries builtin.help and system.intent.
Evidence: go test ./internal/genui/ ./internal/surfacesvc/ ./internal/server/
Impact: Surface buttons may bind help/intent; button-entrance intent
matches only and does not nest-dispatch write commands.
Refs: docs/proposals/2026-10-12-generative-ui-bclass-help-intent.md
Co-authored-by: Cursor <cursoragent@cursor.com>
