Harden HDMI recovery and add tested user installer release tooling

.gitea/workflows/check.yml

@@ -0,0 +1,23 @@
+name: Checks
+on: [push, pull_request]
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install check tools
+        run: sudo apt-get update && sudo apt-get install -y shellcheck jq kbd
+      - name: Shell checks
+        run: |
+          for script in scripts/*.sh lib/*.sh; do bash -n "$script"; done
+          shellcheck -x scripts/*.sh lib/*.sh
+      - name: Behavior tests (unprivileged)
+        run: |
+          if [ "$(id -u)" = 0 ]; then
+            useradd -m revive-test
+            chmod o+x "$HOME"
+            chmod -R a+rX .
+            runuser -u revive-test -- python3 -B -m unittest discover -s tests -v
+          else
+            python3 -B -m unittest discover -s tests -v
+          fi