feat: publish blind-fill MCP as shellgate-secrets npm package

[matthiastjong]

Summary

• Adds packages/shellgate-secrets/ — a standalone npm package that replaces the manual Content-Length stdio framing in blind-fill.mjs with @modelcontextprotocol/sdk (McpServer + StdioServerTransport)
• Claude Code cannot connect to MCP servers using manual framing (stays "pending") — the SDK transport is required
• Tool logic (CDP connection, vault secret fetching, DOM injection, origin validation, keyboard events) is unchanged
• Reverts the previous esbuild bundle approach (fix: use @modelcontextprotocol/sdk for blind-fill MCP server #85) which failed with Dynamic require of "events" is not supported

Usage

npx -y shellgate-secrets

Claude Code config:

{
  "shellgate-secrets": {
    "command": "npx",
    "args": ["-y", "shellgate-secrets"],
    "env": {
      "SHELLGATE_URL": "https://...",
      "SHELLGATE_TOKEN": "sg_..."
    }
  }
}

Test plan

• npm publish from packages/shellgate-secrets/
• npx -y shellgate-secrets starts without errors (with env vars set)
• claude mcp add shellgate-secrets npx -- -y shellgate-secrets → status "connected"
• blind_fill and blind_type tools work with vault secrets + browser target
• Main Shellgate Docker build still passes (no changes to main app)

🤖 Generated with Claude Code