Add comprehensive guidance on avoiding CI failure cycles

Created .claude/docs/avoiding-ci-failure-cycles.md with:
- Analysis of the CI failure whack-a-mole pattern from PR #2114
- The 15-Minute Rule: test locally before pushing
- Red flags indicating you're using CI as a test environment
- Comprehensive checklists for large-scale changes
- Case study showing how 19 fix commits could have been 1 commit

Updated CLAUDE.md to prominently feature this guidance:
- Added "AVOIDING CI FAILURE CYCLES" section after critical requirements
- Highlighted the 15-Minute Rule
- Listed red flags to watch for
- Mandatory local testing checklist for infrastructure changes

Also fixed react_on_rails/.rubocop.yml paths:
- Removed react_on_rails/ prefix from paths (file is now inside that dir)
- Updated exclude patterns to be relative to the .rubocop.yml location

Real Data: 63% of recent commits were "Fix" commits (19/30), showing
clear pattern of using CI as test environment rather than testing locally.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808