fix(server): cache health probes, surface SSE marshal errors, fail closed on missing duties

Health checks reuse a two-second snapshot and bound the schema query. Task SSE writes an error frame when an event cannot be encoded. ResolveDocTask errors when the frozen plan has no duty row, while explicit none-duties stay zero. Drop the unwired semantic-summary replace env, record the intentional dev versus release model split, document the test/main cutover path, and archive pre-goose SQL.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/workflow/runtime/orchestrator.go

@@ -66,6 +66,7 @@ func (o *Orchestrator) ResolveDocTask(ctx context.Context, projectID, docTaskIns
 					res.TemplateVersion = def.TemplateVersion
 				}
 			}
+			matchedDuty := false
 			for _, stPlan := range plan.Stages {
 				if stPlan.StageKey != st.StageKey {
 					continue
@@ -77,8 +78,12 @@ func (o *Orchestrator) ResolveDocTask(ctx context.Context, projectID, docTaskIns
 					res.AuthorUserID = dtPlan.Duties.AuthorUserID
 					res.ReviewerUserID = dtPlan.Duties.ReviewerUserID
 					res.ApproverUserID = dtPlan.Duties.ApproverUserID
+					matchedDuty = true
 				}
 			}
+			if !matchedDuty {
+				return nil, fmt.Errorf("orchestrator: frozen plan has no duties for stage %s task %s", st.StageKey, dt.TaskKey)
+			}
 			return res, nil
 		}
 	}