cleanup: delete obsolete test files instead of disabling them

Removed files that were testing deleted AI functionality:
- cmd/extension_test.go.disabled
- cmd/server_test.go.disabled
- console/atest-ui/src/views/__test__/ai-components.spec.ts.disabled
- pkg/server/ai_http_integration_test.go.disabled
- pkg/server/ai_integration_test.go.disabled

These test files were testing AI components that have been moved to
separate plugin repositories as part of the decoupled architecture.
Deleting them completely rather than keeping disabled copies reduces
codebase clutter and maintenance overhead.

Kept AI protocol buffer tests and interface definitions since these
are needed for communication with AI plugins.

Author: KariHall619