wit_create_work_item fails with misleading "System.Title" error in v2.6.0

[callumdeeley]

Describe the bug
Since upgrading to @azure-devops/mcp@2.6.0, calling wit_create_work_item always fails with the following error, regardless of which fields are passed:
Error creating work item: Operation of changing value type is not supported for the field System.Title

This error is misleading - System.Title is a plain text field and its value is a simple string. The error normally appears in ADO when System.AreaPath or System.IterationPath are included in the initial create call, but in this case neither path field is being passed.

Downgrading to 2.5.0 resolves the issue immediately with no other changes.

To reproduce
Call wit_create_work_item with the minimal possible payload - just a title:

{
  "project": "Platform",
  "workItemType": "Feature",
  "fields": [
    { "name": "System.Title", "value": "Test work item" }
  ]
}

Expected behavior
Work item is created successfully and the new item ID is returned.

Actual behavior
MCP Tool Error Response: Error creating work item: Operation of changing value type is not supported for the field System.Title

Environment

• @azure-devops/mcp version: 2.6.0
• Invoked via: npx -y @azure-devops/mcp@2.6.0
• ADO organisation: on-premises
• Work item types tested: Feature, Product Backlog Item
• Read operations (queries, wit_get_work_item, etc.) are unaffected - only creation is broken

Additional context

• The same call works correctly on 2.5.0 with no other changes
• Work items were being created successfully earlier the same day before npx pulled down 2.6.0
• The error does not change when additional fields (Priority, ValueArea, Tags) are added or removed

[tskimmett]

Yep