implement six-skill gstack 2 runtime

.devcontainer/Dockerfile

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+FROM oven/bun:1.3.14-debian@sha256:9dba1a1b43ce28c9d7931bfc4eb00feb63b0114720a0277a8f939ae4dfc9db6f
+
+ENV DEBIAN_FRONTEND=noninteractive
+ENV PLAYWRIGHT_BROWSERS_PATH=/opt/playwright-browsers
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+      bash ca-certificates curl git jq nodejs npm poppler-utils fonts-liberation \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install the exact Playwright release locked by this repository, including
+# Chromium and its Linux shared-library/font dependencies. The runtime smoke
+# below drives this browser rather than merely checking that a launcher exists.
+RUN bunx playwright@1.58.2 install --with-deps chromium \
+    && chmod -R a+rX /opt/playwright-browsers \
+    && rm -rf /root/.bun/install/cache
+
+WORKDIR /workspaces/gstack
+
+RUN git config --system --add safe.directory /workspaces/gstack

.devcontainer/devcontainer.json

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+{
+  "name": "GStack 2",
+  "build": {
+    "dockerfile": "Dockerfile",
+    "context": ".."
+  },
+  "remoteUser": "root",
+  "postCreateCommand": "bun install --frozen-lockfile",
+  "containerEnv": {
+    "PLAYWRIGHT_BROWSERS_PATH": "/workspaces/gstack/.cache/ms-playwright"
+  },
+  "customizations": {
+    "vscode": {
+      "extensions": []
+    }
+  }
+}