Enforce unique doc filenames and simple wiki-links

Rename section index files to match their titles (tutorials.md,
reference.md, how-to.md, explanation.md) so all filenames are unique.
Convert all path-based wiki-links to simple filename format for better
obsidian.nvim compatibility.

Update doc-filenames task to no longer skip index.md files.
Update doc-links task to reject path-based links containing '/'.

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

docs/reference/reference.md

@@ -59,7 +59,7 @@ Cluster configuration and application registry.
 
 Configuration management for [[indri]]-hosted services.
 
-- [[reference/ansible/roles | Roles]] - Available ansible roles
+- [[roles]] - Available ansible roles
 
 ## Storage
 

docs/reference/services/devpi.md

@@ -32,6 +32,6 @@ Root password stored in 1Password (blumeops vault), injected via ExternalSecret.
 
 ## Related
 
-- [[how-to/use-pypi-proxy]] - Client configuration and package uploads
+- [[use-pypi-proxy]] - Client configuration and package uploads
 - [[argocd]] - Deployment
 - [[1password]] - Secrets management