Address PR feedback: Add assertions and cleanup

- Add assertions to test methods to ensure non-zero results:
  * scripts/images_test.go: Test_EnumerateImages
  * scripts/instancetypes_test.go: Test_EnumerateInstanceTypesSingleRegion, Test_EnumerateGPUTypes
  * integration_test.go: TestIntegration_GetInstanceTypes, TestIntegration_GetImages
- Remove debug statements from production code (client.go, instancetype.go, credential.go, instance.go)
- Remove emojis from test output (smoke_test.go, integration_test.go)
- Remove unused extractOSFamily function from image.go
- Delete unnecessary markdown files (keep only README.md)
- Remove .gitignore for markdown files

Generated with Claude Code

Co-Authored-By: Claude <[email protected]>

Author: liveaverage