feat: add containerized MCP proxy example

[ResultantDesign]

Summary

• Adds examples/container-proxy/ — a Podman/Docker containerized deployment of the Stitch MCP proxy
• API key injected via container secrets (/run/secrets/), not environment variables
• Includes Containerfile, proxy script, and MCP client configuration examples (Claude Code, Cursor, VS Code)

Motivation

The existing run-proxy.ts example requires Node.js and npm on the host. This containerized alternative:

• No host dependencies — Node.js and packages stay inside the container
• Secret isolation — API key read from /run/secrets/, never exposed in env vars or CLI args
• Reproducible — Same image, same behavior everywhere
• Disposable — --rm cleans up after each session

Usage

podman build -t stitch-mcp .
printf '%s' "your-key" | podman secret create stitch-api-key -
podman run --rm -i --secret stitch-api-key stitch-mcp

Test plan

• podman build -t stitch-mcp . succeeds
• podman run --rm -i --secret stitch-api-key stitch-mcp connects and discovers 12 tools
• Verified as MCP server in Claude Code via settings.json configuration

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[davideast]

Thank you @ResultantDesign! Can you sign the CLA? Then we'll merge!