Runs a command and reads the telemetry that run just emitted, returning a `verify-behavior` receipt (confirms / contradicts / ambiguous / null) that grades a behavioral assertion — span count, parent/child structure, duration, error-path status, fan-out, attribute cardinality, ordering — against the observed spans, never against the diff read back. Inputs are a command plus an expectation set. Walks two cheapest-first rungs (an in-memory/file exporter, then `dash0 -X otlp proxy --agent-mode` plus `dash0 spans query`), stamps two-layer run identity, and self-skips when the repo has no Observability Profile dev target. Vendor-neutral: OTLP is the contract, Dash0 one implementation of the read. Use when a fan-out count, a retry that fired twice, an error swallowed into a 200, an N+1, or an unbounded cardinality needs proof from a real run rather than a reading of the code. Triggers only on an explicit ask — "observe this run's telemetry", "prove this behavior with a trace", "/observe-run".