feat(assign): let leads manually assign operators + sync Jira; send platform as Jira label

Adds GET /users/operators (leads+admin) and wires a lead-only assign
control into the test detail header, calling the existing but
previously unreachable POST /tests/{id}/assign endpoint. Manual
assignment now also pushes the Jira ticket assignee immediately
instead of waiting for the operator to start execution.

Also adds test.platform as a kebab-case label on Jira ticket creation.

frontend/src/components/test-detail/TestDetailHeader.tsx

@@ -19,8 +19,10 @@ import {
 import { useMutation } from "@tanstack/react-query";
 import { requestDiscussion } from "../../api/tests";
 import type { Test, TestState, User, DataClassification } from "../../types/models";
+import type { OperatorOut } from "../../api/users";
 import LiveTimer from "./LiveTimer";
 import DataClassificationBadge from "./DataClassificationBadge";
+import AssigneeControl from "./AssigneeControl";
 
 // ── Progress steps ─────────────────────────────────────────────────
 
@@ -90,6 +92,9 @@ interface TestDetailHeaderProps {
   isTogglingHold: boolean;
   onUpdateClassification: (value: DataClassification) => void;
   isUpdatingClassification: boolean;
+  operators: OperatorOut[];
+  onAssignOperator: (side: "red" | "blue", userId: string | null) => void;
+  isAssigningOperator: boolean;
 }
 
 // ── Component ──────────────────────────────────────────────────────
@@ -114,6 +119,9 @@ export default function TestDetailHeader({
   isTogglingHold,
   onUpdateClassification,
   isUpdatingClassification,
+  operators,
+  onAssignOperator,
+  isAssigningOperator,
 }: TestDetailHeaderProps) {
   const role = user?.role ?? "";
   const currentIdx = STATE_INDEX[test.state];
@@ -539,6 +547,24 @@ export default function TestDetailHeader({
             <p className="mt-1 text-sm text-gray-400">
               Created {formatDate(test.created_at)}
             </p>
+            <div className="mt-1.5 flex items-center gap-1.5">
+              <AssigneeControl
+                side="red"
+                assigneeId={test.red_tech_assignee}
+                operators={operators}
+                canEdit={role === "red_lead" || role === "admin"}
+                isSaving={isAssigningOperator}
+                onAssign={(userId) => onAssignOperator("red", userId)}
+              />
+              <AssigneeControl
+                side="blue"
+                assigneeId={test.blue_tech_assignee}
+                operators={operators}
+                canEdit={role === "blue_lead" || role === "admin"}
+                isSaving={isAssigningOperator}
+                onAssign={(userId) => onAssignOperator("blue", userId)}
+              />
+            </div>
             {renderValidationIndicators()}
           </div>
         </div>