Dispatch the agent's release simulation suite against a candidate revision

Dispatch the agent's configured release suite pinned to revision_id.

Phase 1 is advisory: this returns the SimulationSuiteRun handle stamped release_eval_status='pending'. Once every child session's evals settle, the eval task's barrier rolls up a verdict onto the same row (poll GET /v1/sim-suites/{suite_id}/runs/{suite_run_id}).