Minimal-experiment selector (smallest blast-radius test that confirms/refutes)

[CodeBuildder]

Context

Selects the lowest-blast-radius chaos scenario that can confirm or refute the hypothesis. Parent: #29.

Acceptance Criteria

• Selector ranks available scenarios by blast_radius queried from GET /blast-radius
• Chosen scenario is the lowest-blast option targeting the hypothesis subject
• Selection rationale is stored in the experiment record
• Unit test: 3 scenarios with different blast radii → selector picks the smallest

Dependencies

Blocked by: none | Blocks: none

Notes

No model tier. Uses world model blast-radius API.