Enforce unique doc filenames and simple wiki-links (#109)

## Summary
- Rename section index files to match their titles (tutorials.md, reference.md, how-to.md, explanation.md) so all filenames are unique
- Convert all ~47 path-based wiki-links to simple filename format across 15 files
- Update doc-filenames task to no longer skip index.md files
- Update doc-links task to reject path-based links containing '/'

This ensures all wiki-links work correctly in obsidian.nvim by making links resolvable by filename alone.

## Testing
- `mise run doc-filenames` - all unique
- `mise run doc-links` - no broken or path-based links
- `mise run doc-titles` - no duplicates

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/109

docs/tutorials/ai-assistance-guide.md

@@ -62,9 +62,9 @@ Types (file suffix): `.feature`, `.bugfix`, `.infra`, `.doc`, `.ai`, `.misc`
 ### Wiki-Link Formatting
 
 Use simple wiki-links without alternate text or extra spaces:
-- Prefer `[[borgmatic]]` over `[[borgmatic | Borgmatic]]`
+- Prefer `[[borgmatic]]` over `[[borgmatic|Borgmatic]]`
 - Only use alternate text when grammatically warranted (e.g., `[[cluster|Kubernetes]]` reads better than `[[cluster]]`)
-- No spaces around the pipe: `[[path|Text]]` not `[[ path | Text ]]`
+- No spaces around the pipe: `[[path|Text]]` not `[[ path|Text ]]`
 
 When editing documentation, rewrite links to follow this convention as you encounter them.
 
@@ -108,7 +108,7 @@ For ArgoCD operations, use the `argocd` CLI directly:
 
 For AI agents building context:
 
-- [[reference/index|Reference Index]] - Entry point for technical details
+- [[reference|Reference]] - Entry point for technical details
 - [[hosts|Host Inventory]] - What hardware exists
 - [[apps|ArgoCD Apps]] - What's deployed in Kubernetes
 - [[routing|Routing]] - How services are exposed