Panel spec keeps the installation's other panels

Saving panels replaces the whole list, so the spec's setup deleted every
panel it had not created — and with it the credential of the screen on
it. It now appends to the stored list and puts the original back in
teardown, which also removes its own panel.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013Gf7WaExcJ9bs3kfJXB3nK

frontend/tests/panel.spec.ts

@@ -1,4 +1,5 @@
 import { expect, test } from "@playwright/test"
+import type { PanelDef } from "../src/client"
 import { api, apiPage, deleteAll } from "./utils/api"
 
 /**
@@ -16,6 +17,8 @@ import { api, apiPage, deleteAll } from "./utils/api"
 const flowName = `test_panel_${Date.now().toString(36)}`
 const first = `${flowName}_a`
 const second = `${flowName}_b`
+/** The installation's own panels, put back by the teardown. */
+let panels: PanelDef[] | null = null
 
 test.use({ storageState: "playwright/.auth/user.json" })
 test.describe.configure({ mode: "serial" })
@@ -69,16 +72,33 @@ test.beforeAll(async ({ browser }) => {
     })
   }
 
+  // Saving is a whole-list replace, and a panel that disappears takes the
+  // credential of the screen hanging on it. So append to what is there, and
+  // keep the list for the teardown to put back.
+  const config = await (await api(page, "/panels/")).json()
+  const existing: PanelDef[] = (config.panels ?? []).filter(
+    (p: PanelDef) => p.id !== flowName,
+  )
+  panels = existing
   await api(page, "/panels/", {
     method: "PUT",
     data: {
-      panels: [{ id: flowName, title: "Hall", dashboards: [first, second] }],
+      panels: [
+        ...existing,
+        { id: flowName, title: "Hall", dashboards: [first, second] },
+      ],
     },
   })
   await page.close()
 })
 
 test.afterAll(async ({ browser }) => {
+  // Restoring the list is also what removes this spec's own panel.
+  if (panels) {
+    const page = await apiPage(browser)
+    await api(page, "/panels/", { method: "PUT", data: { panels } })
+    await page.close()
+  }
   await deleteAll(browser, [
     `/dashboards/${first}`,
     `/dashboards/${second}`,