Add registry discovery smoke coverage

[adohe]

Spec candidate: #4.

Scope

• Add a CPU smoke test that documents how built-in algorithms and model adapters can be discovered through current registries.
• Keep assertions narrow and stable.
• Avoid importing CUDA-heavy runtime modules.

Acceptance

• Test passes without CUDA, model downloads, or network access.
• Covers discovery behavior, not every model implementation.
• No public API changes.