[e2e-scan] Test: Improve e2e coverage for organization role control plane entity references (expand scenario)

### Gap Summary

Organization role assignments support three entity type references: **APIs**, **Portals**, and **Control Planes**. The existing `org/teams/roles` scenario tests the first two (APIs with literal wildcard `entity_id: "*"` and Portals with `entity_id: !ref` cross-resource reference), but never exercises **Control Planes** as an entity type. This leaves the control plane mapping in `RoleEntityResourceType` unverified end-to-end.

This matters because:
- Control planes are a primary Konnect resource, and role-based access to them is a core RBAC pattern.
- The `RoleEntityResourceType` function in `role_entity.go` explicitly maps `"controlplane"` / `"controlplanes"` to `ResourceTypeControlPlane`, but this mapping is never exercised through a complete plan → apply → diff → verify cycle.
- A regression in control plane entity reference resolution (validation, planning, or execution) would go undetected by the current E2E suite.
- The system account and user role scenarios (`org/system-accounts/assignments`, `org/users/assignments`) also only test APIs and Portals entity types, so adding control plane coverage for team roles would validate the shared `ValidateRoleEntityReference` and `roleEntityDependency` code paths for all three assignment types.

### Evidence

- **Code support**: `internal/declarative/resources/role_entity.go:14-18` maps control plane entity type names to `ResourceTypeControlPlane`.
- **Existing coverage**: `test/e2e/scenarios/org/teams/roles/scenario.yaml` step 001 tests `entity_type_name: APIs`, step 008 tests `entity_type_name: Portals`.
- **Missing**: No scenario in `test/e2e/scenarios/org/` uses `entity_type_name: Control Planes` or references a control plane in a role assignment.
- **Shared validation**: `ValidateRoleEntityReference` in `role_entity.go:53-87` handles all entity types uniformly — testing with control planes validates the full type mapping path.

### Proposed Scenario Work

**Expand the existing `org/teams/roles` scenario** by adding a new overlay and step that parallels the portal entity ref pattern (step 008) but uses a control plane entity reference instead.

**Add an overlay** at `test/e2e/scenarios/org/teams/roles/overlays/005-cp-entity-ref/config.yaml`:
```yaml
_defaults:
kongctl:
namespace:

control_planes:
- ref:
name:
description: Control plane for team role entity ref E2E scenario

organization:
teams:
- ref:
name:
description: Team for control plane role entity ref E2E
roles:
- ref:
role_name: Viewer
entity_id: !ref #id
entity_type_name: Control Planes
entity_region: us
```

**Add a scenario step** (e.g., step `009-plan-cp-entity-ref`) that:
1. Loads the overlay with a control plane and team with a role referencing it
2. Runs `plan --mode apply`
3. Asserts the plan shows 3 CREATE changes (control plane, team, role)
4. Asserts the role change has `fields.entity_id: "__REF__:#id"` and `fields.entity_type_name: Control Planes`
5. Asserts the role `depends_on` includes the control plane resource

Add corresponding vars to the scenario header for the control plane refs, names, and namespace.

### Acceptance Criteria

- [ ] New overlay creates a control plane resource and a team role with `entity_type_name: Control Planes`
- [ ] Role uses `!ref #id` as `entity_id` to test cross-resource reference resolution
- [ ] Plan step asserts correct resource type, action, entity fields, and dependency chain
- [ ] The `depends_on` assertion confirms the role depends on the control plane resource
- [ ] The step follows the same plan-only pattern as the existing portal entity ref step (step 008), avoiding extra resource creation and cleanup

### Reference Patterns

- `test/e2e/scenarios/org/teams/roles/scenario.yaml` step 008 (`plan-portal-entity-ref`) — demonstrates the exact same pattern for portal entity references, including the overlay structure and assertion style
- `test/e2e/scenarios/org/teams/roles/overlays/004-portal-entity-ref/config.yaml` — template for the control plane overlay structure

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> - [x] expires on Oct 16, 2026, 4:58 AM UTC

Start with test/e2e/scenarios/org/teams/roles/scenario.yaml step 008 and its overlay at overlays/004-portal-entity-ref/config.yaml. Add the control-plane overlay and corresponding plan-only step, then verify the plan reports three creates, the control-plane entity reference fields, and the dependency on the control plane resource.

Written by the indexing model from the issue text.