Add the optional Playwright web UI smoke test

docs/testing.md

@@ -177,6 +177,21 @@ Notes:
   locally and point `LD_LIBRARY_PATH` at it.
 - The live start was verified on 2026-09-13 through the web UI route.
 
+## Web UI browser smoke test
+
+Optional. `playwright-core` is an optional dependency and the test needs a Chromium (`PW_CHROMIUM`,
+or a Playwright cache under `~/.cache/ms-playwright`). The daemon must be running with media data.
+
+```sh
+cd poc
+pnpm test:ui
+VESKSLOP_UI_URL=https://192.168.0.178:8789/ pnpm test:ui
+```
+
+It opens the Media tab, loads tiles, verifies no broken images, applies the cached-only filter,
+checks that the zoom slider changes the grid density, presses Reset, and fails on any console
+error. A screenshot lands in `/tmp/opencode/ui-smoke.png`.
+
 ## Slopbot live check
 
 The bot core needs a real token and an invite to the test guild. The check logs in, lists guilds,