Runtime API: expose verifier evidence beyond the verifier_failed counter #5073

Problem

The v0.9.4 Fleet projection exposes only aggregate verifier state such as verifier_failed. A managed client cannot inspect which verifier ran, what evidence it produced, why it failed, whether it is retryable, or how the result relates to a task/run.

This is a capability-parity follow-up, not a v0.9.4 launch blocker.

Live evidence

• Aggregate Fleet status projection at 92128e6: runtime_api.rs
• The route table exposes Fleet runs and workers, but no verifier resource or evidence endpoint: runtime_api.rs

Scope

• Add a typed verifier receipt linked to run/task/worker IDs.
• Expose verifier identity/version, bounded inputs, status, timestamps, redacted evidence/artifacts, failure class, and retry eligibility.
• Add read/list/inspect first; any rerun/cancel action must delegate to the existing execution owner and preserve approvals.
• Keep raw logs/artifacts behind explicit inspection and redaction.
• Add event replay and durable receipt tests.

Done when

A managed client can explain a verifier failure and navigate to its evidence without inferring state from a counter or scraping logs.