fix: Add default sort value to create_collection

Collections without sort field cause frontend error:
"Cannot read properties of null (reading 'field')"

Now sets {"field": "index", "direction": "asc"} as default.

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

CHANGELOG.md

@@ -2,6 +2,15 @@
 
 All notable changes to this project will be documented in this file.
 
+## [1.3.8] - 2026-01-31
+
+### Fixed
+
+- **Collection Sort Field:** `create_collection` now sets default `sort` value
+  - Was: `sort` column left NULL, causing frontend error "Cannot read properties of null (reading 'field')"
+  - Now: Sets `{"field": "index", "direction": "asc"}` as default
+  - Outline frontend requires this field to render collections
+
 ## [1.3.7] - 2026-01-31
 
 ### Fixed