S1450 -- Private fields only used as local variables should become local variables

[vdebellabre]

Source: S1450

Candidate rule from Rules to work on.md. Review for relevance to Creedengo's green-coding scope, then implement if kept.

Checklist

• Confirm not already covered by CAxxxx / SYSLIB1xxx
• Decide green-coding relevance (perf / allocation / energy impact)
• Pick the Creedengo GCIxx id
• Implement analyzer + tests
• Implement code fixer (if applicable)
• Update docs