Add configurable protection for most recent N tool calls

[Tarquinen]

Summary

Add a config option to protect the most recent N tool calls from being pruned by AI analysis, while still allowing deduplication.

Proposed Config

{
  "protectRecentTools": 5  // Last 5 tool calls protected from AI pruning
}

Rationale

Recent tool outputs are more likely to be contextually relevant. This provides a safeguard independent of semantic analysis, while still allowing deduplication to remove obvious duplicates.

Implementation Notes

• Apply filter in janitor.ts after deduplication phase, before AI analysis
• Deduplication should still be allowed to prune within the last N tools
• Should work alongside existing protectedTools array