Add Phase 3 tutorials with audience targeting (#94)

## Summary
- Create tutorials directory structure with index page
- Add 5 main tutorials targeting different audiences:
  - **what-is-blumeops** (Reader, AI) - High-level orientation
  - **exploring-the-docs** (All) - Navigation guide
  - **ai-assistance-guide** (AI, Owner) - Context for AI-assisted operations
  - **contributing** (Contributor) - First contribution workflow
  - **replicating-blumeops** (Replicator) - Overview for building similar setup
- Add 4 replication sub-tutorials:
  - tailscale-setup, kubernetes-bootstrap, argocd-config, observability-stack
- Update README.md to mark Phase 3 complete
- Add changelog fragment

Each tutorial explicitly identifies its target audiences and links to reference material rather than re-explaining concepts.

## Deployment and Testing
- [x] All pre-commit hooks pass (doc-links validates wiki links)
- [ ] Build docs via workflow to verify rendering
- [ ] Review content for accuracy

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/94

docs/index.md

@@ -4,8 +4,13 @@ title: blumeops-documentation
 
 Welcome to the BlumeOps documentation.
 
-[[README | Documentation Home]] - Temporary home while docs are being restructured (see [Diataxis](https://diataxis.fr/) restructuring plan)
+**New here?** Start with [[exploring-the-docs]] to find your way around.
 
 ## Sections
 
-- [[reference/index | reference]] - Technical reference cards for services, infrastructure, and operations
+- [[tutorials/index | Tutorials]] - Learning-oriented guides for getting started
+- [[reference/index | Reference]] - Technical reference cards for services, infrastructure, and operations
+
+## About
+
+[[README | Documentation Home]] - Restructuring plan and changelog info