chore: consolidate IDEAS.md and bump version to 3.3.1

- IDEAS.md: Reduce from 12 to 4 actionable research topics
- Unified "MCP Security Hardening" (merged 3 overlapping topics)
- Expanded Discarded section (3 → 16 entries with justifications)
- Technical writer agent validation against reference.yaml
- Version bump: 3.3.0 → 3.3.1 across all docs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

guide/cheatsheet.md

@@ -6,7 +6,7 @@
 
 **Written with**: Claude (Anthropic)
 
-**Version**: 3.2.0 | **Last Updated**: January 2026
+**Version**: 3.3.1 | **Last Updated**: January 2026
 
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guide/ultimate-guide.md

@@ -10,7 +10,7 @@
 
 **Last updated**: January 2026
 
-**Version**: 3.2.0
+**Version**: 3.3.1
 
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