The pr_pass/pr_fail ActionSpecs carry self_review_block=True, but
_gate_preflight never populated Context.original_developer_slug, and
actor_slug was read off agent.slug — which GatewayAgentView does not
carry, so it was always None in production. The block was structurally
dormant: a reviewer who was also the original developer of the
assembled PR could pass (or fail) their own work. The service-layer
_validate_not_self_review backstop only covers qa/documenter, not
pr_reviewer, so the spec gate is the only defense.
Set actor_slug=str(reviewer_agent_id) (GatewayAgentView has no slug,
so the UUID is the identity) and original_developer_slug from the
original_developer marker (a UUID stored as a string). Both resolve to
UUID strings, so the spec's string-equality comparison fires when the
reviewer IS the recorded original developer.
The marker is never set on assembled coordination tasks (only on
dev-leaf tasks at QA/doc claim), so the block stays dormant by design
in production — but the gate is now correctly wired to fire if the
marker were ever set to the reviewer. Zero production behavior change;
the dormant-in-production state is pinned by the no-marker test.
