adding opencode to the environment

.opencode-sandbox/Dockerfile

@@ -0,0 +1,19 @@
+FROM archlinux:latest
+
+# Network restriction — only allow git.processhub.work
+RUN pacman -Syu --noconfirm && \
+    pacman -S --noconfirm \
+      nodejs \
+      npm \
+      git \
+      iptables \
+      opencode \
+    && pacman -Scc --noconfirm
+
+# Firewall script — blocks everything except your Gitea instance
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+
+WORKDIR /workspace
+
+ENTRYPOINT ["/entrypoint.sh"]