improvement: /insights should check for existing CLAUDE.md rules before proposing new ones

Observation: 5 out of 6 friction-reducing rules already exist in learning_with CLAUDE.md.

Problem statement:

• /insights proposes adding rules that are already documented
• Root cause analysis shows: Problem is NOT missing rules, but NON-COMPLIANCE
• This wastes context and confuses CLAUDE.md as single source of truth

Examples from 223-session analysis:

• WT enforcement: documented in CLAUDE.md > ignored by 10% of subagents
• TDD mandatory: documented > violated by bug-fix tasks
• Review steps: documented in RDD > skipped when under time pressure
• Migration safety: documented > violated without migration number check

Proposal: Enhance /insights to:

1. Before proposing new rules, check existing CLAUDE.md for related rules
2. If found, analyze WHY the rule is not being followed:

• Is it hard to understand?
• Is it in wrong section/format?
• Is it conflicting with other rules?
• Is it unclear when to apply?

1. Propose IMPROVEMENTS to existing rules instead of NEW rules
2. When new rule is genuinely needed, explicitly state why existing rules don't cover it

This improves CLAUDE.md signal-to-noise ratio and focuses improvements on compliance, not documentation.