feat(FN-2556): add TaskForm bottom slot for model configuration

- Add a new renderBelowModelConfiguration prop in TaskForm and render it beneath the Model Configuration section inside More options
- Update TaskDetailModal to use the new slot so the Source Issue edit block appears below model settings instead of near the primary section
- Adjust TaskDetailModal source-issue edit tests to expand More options before interacting with source fields
- Add ordering assertions in TaskForm and TaskDetailModal tests to verify the injected block sits between Model Configuration and Workflow Steps

packages/dashboard/app/components/TaskForm.tsx

@@ -90,6 +90,8 @@ export interface TaskFormProps {
 
   /** Optional content to render between the primary section and the "More options" toggle. */
   renderBelowPrimary?: React.ReactNode;
+  /** Optional content to render inside "More options" below Model Configuration. */
+  renderBelowModelConfiguration?: React.ReactNode;
   /** When true, skip rendering the Dependencies form-group inside "More options". Use when the parent renders its own dependency UI via renderBelowPrimary. */
   hideDependencies?: boolean;
   /** When true (default), More options auto-expands when non-default advanced selections are present. */
@@ -133,6 +135,7 @@ export function TaskForm({
   onSubtaskBreakdown,
   onClose,
   renderBelowPrimary,
+  renderBelowModelConfiguration,
   hideDependencies,
   autoExpandMoreOptionsOnSelection = true,
   reviewLevel,
@@ -1052,6 +1055,8 @@ export function TaskForm({
         )}
       </div>
 
+      {renderBelowModelConfiguration}
+
       {/* Workflow Steps */}
       <div className="form-group" data-testid="workflow-steps-section">
         <label>Workflow Steps</label>