[danmayer]

Summary

• remove the misspelled Coverband::Utils::Results#runtime_relavent_lines method and document #runtime_relevant_lines as the required 7.0 replacement
• replace the shipped 1,092-line ActiveSupport cache implementation plan with a concise decision record while keeping the existing filename and inbound link valid
• remove or clarify the remaining stale TODO comments under lib/
• remove the stale Coveralls badge from the README and the Coveralls link from docs/resources.md
• delete the obsolete publish_gem rake task that hard-coded and manually pushed a 4.2.3 package; Bundler rake release remains the supported release path
• pin the test matrix, StandardRB, JavaScript, and diagram workflows to Ubuntu 24.04 instead of ubuntu-latest; this intentionally makes runner upgrades manual and renames matrix checks to test (ubuntu-24.04, ...)
• add the previously missing final newline to the diagram workflow

Items 1-9 from the release survey otherwise landed in #671; this is one focused follow-up PR for the remaining Coverband 7 cleanup.

Verification

• bundle exec ruby -Ilib:test test/coverband/utils/results_test.rb (14 runs, 6,350 assertions, 0 failures, 0 errors)
• bundle exec rake test (629 runs, 7,985 assertions, 0 failures, 0 errors, 4 skips)
• bundle exec standardrb --format github
• node --test test/javascript/*.test.mjs (13 tests, 0 failures)
• bundle exec rake build (coverband-7.0.0.gem builds successfully)
• Rails demo app against the local Coverband 7.0 checkout (97 runs, 218 assertions, 0 failures, 0 errors)
• manual Rails demo smoke test of the coverage report and views, routes, and translations tracker pages
• git diff --check

The repository currently has no required status-check names on main, so the Ubuntu runner label change does not break branch protection.