[danmayer]

Summary

• remove the global JSON 2 development constraint from the gemspec
• scope JSON 2 to Rails 7.0–8.0 test bundles whose ActiveSupport releases are incompatible with JSON 3
• add a dedicated latest-Rails/JSON 3 CI lane
• require a JSON-3-compatible, security-fixed MCP development dependency
• bump the prerelease version to 7.0.0.rc.2

Consumer impact

The built gem has no runtime JSON dependency. Applications installing Coverband remain free to resolve JSON 2 or JSON 3.

Validation

• default bundle resolves JSON 3.1.0
• 629 tests, 7,985 assertions, 0 failures, 4 skips
• 7 forked tests, 44 assertions, 0 failures
• StandardRB clean
• built gem dependency inspection confirms JSON is absent