docs: design Compass Code Graph v1

[forhappy]

Summary

• define the first supported compass.graph/1 contract using a versioned NetworkX-compatible envelope
• specify the closed core and enterprise node/edge vocabulary, including canonical routes_to relationships
• define provenance, identity, hard-cutover, framework-routing, Program IR, query, VS Code, and release-qualification behavior
• add a 19-task implementation-first plan with current-state context, exact ownership boundaries, downstream contracts, verification, and completion criteria

Why

Compass is the enterprise code-intelligence product, so its graph contract must be reliable, explainable, and consistent across languages and clients before implementation begins. These documents establish the approved architecture and implementation sequence without introducing a legacy adapter or changing Graphify.

Impact

Documentation only. This PR does not change runtime behavior or begin implementation. It gives future implementation work a single approved contract and a reviewable delivery sequence.

Validation

• confirmed the branch diff contains only the design and implementation-first plan
• ran git diff --check origin/main...HEAD
• verified the plan contains 19 contextual implementation tasks
• verified both documents agree on compass.graph/1, routes_to, and the independently versioned Program IR schema