/insights should cross-reference existing CLAUDE.md before suggesting fixes

Problem

The /insights report analyzes historical session data and generates suggestions (e.g., "add Terraform aliases to CLAUDE.md"), but it does not check whether those suggestions have already been addressed in the user's current configuration.

For example, my global ~/.claude/CLAUDE.md already documents Terraform aliases (tfinit, tfplan, tfapply, etc.) and working directory conventions. Despite this, the insights report still recommended adding these exact conventions — making the suggestion redundant noise rather than actionable signal.

Expected Behavior

Before generating claude_md_additions suggestions, the insights report should:

1. Read the user's current CLAUDE.md (global and project-level)
2. Cross-reference existing instructions against proposed suggestions
3. Filter out or mark as "already addressed" any suggestions that are already covered
4. Only surface net-new recommendations

Current Behavior

The report generates suggestions purely from historical friction patterns without checking current configuration state, leading to stale/redundant recommendations that undermine trust in the report's usefulness.

Impact

Users who have already acted on friction by updating their CLAUDE.md see the same suggestions repeated, which:

• Reduces confidence in the report's accuracy
• Makes it harder to identify which suggestions are genuinely new and actionable
• Discourages engagement with the insights feature