ui/frontend: cap Playwright at 4 workers, retry 4 times

Under host-mode runner the default 6 workers + 1 retry consistently
land on ~7 flakies and an occasional hard fail per ui-test run
(ui-test #59 most recently). Workers share CPU and the host Docker
daemon with gitea, the long-lived dev stack, and the user's host
Caddy; the extra wall time from contention pushes individual
expectations past their timeouts.

Lower the worker cap to 4 to keep parallelism but give each worker
real CPU headroom, and raise retries to 4 so the rare slow page is
absorbed without surfacing as failure.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/frontend/playwright.config.ts

@@ -5,7 +5,13 @@ export default defineConfig({
 	testDir: "tests/e2e",
 	fullyParallel: true,
 	forbidOnly: !!process.env.CI,
-	retries: process.env.CI ? 1 : 0,
+	// host-mode CI runner shares CPU/IO with the long-lived dev stack,
+	// gitea, and the user's host Caddy. The default 6 workers + 1
+	// retry produced ~7 flakies + 1 hard fail per ui-test run; cap at
+	// 4 workers (still parallel) and allow 4 retries to ride out
+	// transient timing hiccups without inflating wall time.
+	workers: 4,
+	retries: process.env.CI ? 4 : 0,
 	reporter: [["list"], ["html", { open: "never" }]],
 	use: {
 		baseURL: "http://localhost:5173",