ci(jetbrains): install font libs needed by JBR inside container

The JetBrains Runtime bundled with IntelliJ ships libfontmanager.so
but expects libfreetype.so.6 and libfontconfig1 on the host system.
The container image currently lacks these, causing UnsatisfiedLinkError
in any test that initialises Swing font metrics.

Install them explicitly until the updated container image (which will
include these packages in the Dockerfile) is available.

Co-authored-by: kiloconnect[bot] <240665456+kiloconnect[bot]@users.noreply.github.com>

.github/workflows/test-jetbrains.yml

@@ -55,6 +55,9 @@ jobs:
       - name: Mark workspace as git-safe
         run: git config --global --add safe.directory "$GITHUB_WORKSPACE"
 
+      - name: Install font libraries for JBR
+        run: apt-get install -y --no-install-recommends libfreetype6 libfontconfig1 fonts-dejavu-core
+
       - name: Install dependencies
         run: bun install