Add admin control over which entity types and bundles are visible to AI

Problem/Motivation

When an AI agent discovers what it can create, it sees every fieldable entity type and bundle on the site. Many of those are internal, system-managed, or simply not intended for AI authoring, but there was no way for an administrator to limit the catalog. Sites need to scope what agents can see and act on without writing code.

Proposed resolution

Add a settings form at /admin/config/ai/entity-blueprint (under the AI settings menu) where administrators uncheck entity types or individual bundles to hide them from the AI. Selections are stored as hidden_entity_types and hidden_bundles in entity_blueprint_ai.settings.

BundleListBuilder applies this filtering centrally, so a hidden type or bundle never appears in bundle discovery, in the skills catalog, or in advertised schemas — every AI-facing surface honors the same setting. The visible catalog is exposed to agents through the new eb_list_bundles tool (optionally filtered to one entity type).

User interface changes

New admin form "Entity Blueprint AI" under Configuration » AI, listing each fieldable entity type as a collapsible section with a per-type visibility checkbox and per-bundle checkboxes. Requires the administer site configuration permission.

API changes

• New AI tool eb_list_bundles (lists AI-visible entity types and bundles with descriptions).
• Filtering is applied in BundleListBuilder, which also invokes hook_entity_blueprint_ai_bundle_list_alter() for additional programmatic filtering on top of the configured allow/deny.

Data model changes

New config object entity_blueprint_ai.settings with hidden_entity_types (sequence of entity type IDs) and hidden_bundles (mapping of entity type ID to a sequence of bundle IDs). Default install hides nothing.