Add devcontainer setup with Claude Code, thv, and mermaid MCP

.devcontainer/devcontainer.json

@@ -0,0 +1,20 @@
+{
+  "name": "thv + Claude Code",
+  "image": "mcr.microsoft.com/devcontainers/base:ubuntu",
+  "features": {
+    "ghcr.io/devcontainers/features/node:1": {
+      "version": "lts"
+    },
+    "ghcr.io/devcontainers/features/docker-outside-of-docker:1": {}
+  },
+  "postCreateCommand": "bash .devcontainer/setup.sh",
+  "postStartCommand": "bash .devcontainer/start-servers.sh",
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "GitHub.copilot",
+        "GitHub.copilot-chat"
+      ]
+    }
+  }
+}

.devcontainer/setup.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+# Install Claude Code (Node.js provided via devcontainer feature)
+npm install -g @anthropic-ai/claude-code
+
+# Install thv (ToolHive) to ~/.local/bin
+mkdir -p "$HOME/.local/bin"
+curl -fsSL "https://github.com/stacklok/toolhive/releases/download/v0.11.0/toolhive_0.11.0_linux_amd64.tar.gz" \
+  | tar -xz -C "$HOME/.local/bin" thv
+
+export PATH="$HOME/.local/bin:$PATH"
+
+# Ensure Claude Code config exists and onboarding is marked complete
+if [ ! -f "$HOME/.claude.json" ]; then
+  echo '{}' > "$HOME/.claude.json"
+fi
+node -e "
+const fs = require('fs');
+const path = '$HOME/.claude.json';
+const config = JSON.parse(fs.readFileSync(path, 'utf8'));
+config.hasCompletedOnboarding = true;
+config.lastOnboardingVersion = '99.99.99';
+fs.writeFileSync(path, JSON.stringify(config));
+"
+
+# Ensure VS Code Server MCP config exists so thv can register itself
+mkdir -p "$HOME/.vscode-server/data/User"
+if [ ! -f "$HOME/.vscode-server/data/User/mcp.json" ]; then
+  echo '{}' > "$HOME/.vscode-server/data/User/mcp.json"
+fi
+
+# Register clients (Docker not needed for registration)
+thv client register claude-code
+thv client register vscode-server

.devcontainer/start-servers.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+export PATH="$HOME/.local/bin:$PATH"
+
+# Start MCP servers (requires Docker, runs on every Codespace start)
+thv run mermaid 2>/dev/null || true
+thv run fetch 2>/dev/null || true
+thv run osv 2>/dev/null || true
+thv run semgrep 2>/dev/null || true