Add a machine-readable scoring breakdown to JSON output

[Syqens]

Summary

Extend JSON output so it includes a clear breakdown of how the readiness score was computed.

Why

The Markdown report is easy to read, but JSON output should also be useful for automation, comparisons, or future dashboards. Right now consumers can see the final score, but not the detailed reasoning behind it.

Proposed behavior

• include a score breakdown object in JSON output
• expose per-signal weights and whether each signal was present
• include any bonus logic such as setup instructions found in the README

Example shape

The JSON could include the final score plus a per-signal breakdown such as whether readme, contributing, or ci_workflows were present and how much each contributed.

Notes

This keeps the CLI useful for future integrations without changing the human-readable report format.