feat(docker): dodaj runtime stage z web-ext run

- Dodano nowy stage 'runtime' w Dockerfile
- Instalacja Firefox ESR i Xvfb dla headless execution
- Automatyczne uruchomienie web-ext run z Xvfb
- Dodano usługę rentgen_run w compose.yml
- Zaktualizowana dokumentacja z przykładami użycia

Możliwe użycie:
- docker build --target runtime -t rentgen-run .
- docker run --rm -it rentgen-run
- docker compose up rentgen_run

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Dockerfile

@@ -14,6 +14,14 @@
 #   Run commands in the container:
 #     docker run --rm rentgen npm run build:chrome
 #     docker run --rm rentgen npm run typecheck
+#
+#   Run extension in Firefox (headless):
+#     docker build --target runtime -t rentgen-run .
+#     docker run --rm -it rentgen-run
+#
+#   Using docker-compose:
+#     docker-compose up rentgen_check     # Build only
+#     docker-compose up rentgen_run       # Run in Firefox
 
 # Build stage
 FROM node:lts AS builder
@@ -57,3 +65,18 @@ FROM builder
 
 # Default command shows the built artifact
 CMD ["ls", "-lh", "/app/web-ext-artifacts/"]
+
+# Runtime stage - for running extension in Firefox
+FROM builder AS runtime
+
+# Install Firefox and Xvfb for headless execution
+RUN apt-get update && apt-get install -y \
+    firefox-esr \
+    xvfb \
+    && rm -rf /var/lib/apt/lists/*
+
+# Set display for Xvfb
+ENV DISPLAY=:99
+
+# Start Xvfb and run extension in Firefox
+CMD Xvfb :99 -screen 0 1024x768x24 & npm run ext-test

compose.yml

@@ -0,0 +1,10 @@
+services:
+    rentgen_check:
+        build: .
+
+    rentgen_run:
+        build:
+            context: .
+            target: runtime
+        stdin_open: true
+        tty: true