feat(FN-3573): harden plugin setup sync and test-isolation handling

- Add plugin setup API coverage for migration and sync edge cases
- Expand plugin route tests and implementation safeguards for setup state handling
- Update legacy API glue to align plugin setup responses with route behavior
- Keep test-isolation runtime ignore handling compatible with live app activity

Fusion-Task-Id: FN-3573

packages/dashboard/app/api/legacy.ts

@@ -18,6 +18,7 @@ import type {
   WorkflowStepInput,
   WorkflowStepResult,
   PluginInstallation,
+  PluginSetupCheckResult,
   PluginUiSlotDefinition,
   PluginUiContributionDefinition,
   PluginDashboardViewDefinition,
@@ -7763,6 +7764,23 @@ export async function updatePluginSettings(
   });
 }
 
+export type PluginSetupStatusResponse =
+  | { hasSetup: false }
+  | { hasSetup: false; status: Extract<PluginSetupCheckResult, { status: "error" }> }
+  | ({ hasSetup: true } & PluginSetupCheckResult);
+
+/** Fetch plugin setup status */
+export async function fetchPluginSetupStatus(id: string, projectId?: string): Promise<PluginSetupStatusResponse> {
+  return api<PluginSetupStatusResponse>(withProjectId(`/plugins/${encodeURIComponent(id)}/setup-status`, projectId));
+}
+
+/** Trigger plugin setup install hook */
+export async function installPluginSetup(id: string, projectId?: string): Promise<{ success: boolean; error?: string }> {
+  return api<{ success: boolean; error?: string }>(withProjectId(`/plugins/${encodeURIComponent(id)}/setup/install`, projectId), {
+    method: "POST",
+  });
+}
+
 /** Reload a running plugin with updated code */
 export async function reloadPlugin(id: string, projectId?: string): Promise<PluginInstallation> {
   return api<PluginInstallation>(withProjectId(`/plugins/${encodeURIComponent(id)}/reload`, projectId), {