Fix missing .so for playwright e2e

Author: IDisposable

.devcontainer/install-deps.sh

@@ -76,4 +76,9 @@ echo \
   trixie stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
 
 sudo apt update
-sudo apt install docker-ce-cli
+sudo apt install -y --no-install-recommends docker-ce-cli
+
+# Playwright Chromium system libraries (libnspr4, libnss3, libgbm, X11/xcb, etc.)
+# Needed for `make test_e2e` / `npx playwright test` to launch the bundled headless shell.
+# Uses `npx -y` so it runs before `ui/` has been `npm ci`'d.
+sudo env "PATH=$PATH" npx -y playwright@latest install-deps chromium