Initial scaffold: Debian-based opencode v1.4.0 dev container

Dockerfile with Node.js 22, git, ssh, fzf, ripgrep, fd, non-root user.
Entrypoint auto-configures provider from env vars.
docker-compose with workspace mount, SSH keys, and persistent data volume.

docker-compose.yml

@@ -0,0 +1,43 @@
+# opencode-devbox docker-compose
+#
+# Usage:
+#   cp .env.example .env    # configure your provider and keys
+#   docker compose up -d
+#   docker compose exec devbox opencode
+#
+# Or for interactive one-shot:
+#   docker compose run --rm devbox
+
+services:
+  devbox:
+    build:
+      context: .
+      args:
+        INSTALL_PYTHON: "false"
+        INSTALL_GO: "false"
+    image: opencode-devbox:latest
+    container_name: opencode-devbox
+    stdin_open: true
+    tty: true
+    env_file:
+      - .env
+    environment:
+      - TERM=xterm-256color
+    volumes:
+      # Host workspace — mount your project here
+      - ${WORKSPACE_PATH:-.}:/workspace
+
+      # SSH keys (read-only) — for git push/pull
+      - ${SSH_KEY_PATH:-~/.ssh}:/home/developer/.ssh:ro
+
+      # Optional: mount your own opencode config
+      # - ./config/opencode.json:/home/developer/.config/opencode/opencode.json:ro
+
+      # Optional: persist opencode data (auth, memory, etc.)
+      - devbox-data:/home/developer/.local/share/opencode
+
+      # Optional: AWS credentials for Bedrock
+      # - ~/.aws:/home/developer/.aws:ro
+
+volumes:
+  devbox-data: