feat: add --host flag and QMD_HOST env for configurable bind address

[ductiletoaster]

Problem

The MCP HTTP server hardcodes localhost as the bind address in startMcpHttpServer():

httpServer.listen(port, "localhost", () => resolve());

This prevents cross-container access in Kubernetes deployments where QMD runs as a ClusterIP service and other pods need to connect to it.

Solution

Add a configurable bind address with three levels of control:

1. --host CLI flag: qmd mcp --http --host 0.0.0.0
2. QMD_HOST environment variable: QMD_HOST=0.0.0.0 qmd mcp --http
3. API parameter: startMcpHttpServer(8181, { host: "0.0.0.0" })

Priority: options.host > QMD_HOST > "localhost" (default)

Changes

• src/mcp/server.ts: Add host to options, read QMD_HOST env, use in listen() and log message
• src/cli/qmd.ts: Add --host CLI flag, pass through to startMcpHttpServer and daemon spawn args

Backward Compatible

Defaults to localhost — no behavior change for existing users.

Use Case

Running QMD as a Kubernetes service behind an AI gateway (Bifrost) that aggregates multiple MCP servers. The gateway runs in a different namespace and needs TCP access to QMD's HTTP port.

# Kubernetes deployment
containers:
  - name: qmd
    image: node:22-slim
    command: ["qmd", "mcp", "--http", "--host", "0.0.0.0", "--port", "8181"]

Or via environment variable:

env:
  - name: QMD_HOST
    value: "0.0.0.0"