Unsafe environment variable access pattern in create_ci_badge.py

[brianredbeard]

Description

Multiple places use os.environ['VAR'] syntax which raises KeyError if the variable doesn't exist. Should use os.environ.get() with defaults or validation.

Location

https://github.com/validatedpatterns/multicloud-gitops/blob/main/tests/interop/create_ci_badge.py#L29-L60

Expected Behavior

Consistently use os.environ.get() with appropriate defaults or explicit validation.