docs: show AI-assisted daily workflow

[forhappy]

Summary

• retain the abstract README overview that explains Compass's value proposition
• make AI agent integration the primary daily workflow with compass init, compass install, and compass watch
• explain agent auto-detection, the portable Agent Skills fallback, explicit platform selection, and host activation
• describe the installed skill accurately: focused queries first, GRAPH_REPORT.md for repository-wide context, then minimal source inspection
• keep the high-level workspace graph as an optional human-review path
• show all 32 workspace packages, 100 non-development dependency edges, and seven functional areas

Impact

The README now leads developers toward AI-assisted codebase navigation and tells them how to verify or override agent detection. It preserves direct graph exploration for human review. Product behavior and compatibility contracts are unchanged.

Validation

• cargo test -p compass-cli --test install_cli --locked (22 passed)
• cargo metadata --locked --no-deps --format-version 1
• npm test -w @compass/viewer-tests -- graph-parity.spec.ts (8 passed)
• git diff --check

AI assistance

Codex drafted and reviewed the documentation changes. The agent-install claims were verified against the CLI implementation, shipped Compass skill, setup guide, and installer integration tests.