Add interactive learner journey viewer

[dhanson-wp]

Summary

• Add a static, client-side learner journey viewer for Model Context Polytechnic course progress
• Include a 16-bit campus map, animated learner route, demo save file, badges, quest log, and progress controls
• Link the viewer from the docs homepage and support optional live progress loading from a public MCP enrollment key

Notes

• The viewer is intentionally docs-only and does not change MCP server behavior, course scoring, or learner storage
• Demo mode works without credentials; live mode uses the public progress tool when the page can reach the MCP endpoint
• The enrollment key is described as an anonymous course card, not a WordPress password

Checks

• composer lint
• node --check docs/learner-journey.js
• git diff --check