[AzureDevOpsExtension] Add a one-click “Fix” flow to start sessions from Azure DevOps work item descriptions

### Summary

I can open Azure DevOps work items in the canvas, but I cannot easily pass the work item’s **title and description** into a Copilot session to start implementation.

I would like a workflow similar to the existing **Fix** button for pull request comments: one click should load the work item context into the active session

### Environment

App version 1.1.14
Windows 10.0.26200 Build 26200
azure-devops-copilot-plugin 0.1.53

### Problem

When I open a work item in the Azure DevOps canvas, I can view its details, but I still have to manually copy/paste the title and description into chat before starting work.

### Expected behavior

A work item should expose an action like:

- **Fix**

- or **Implement**

That action should send the work item’s title/description to the active session

### Current behavior

- Work items can be opened in the Azure DevOps canvas.

- The work item context is visible there.

- The context is not transferred into the session automatically.

### Why this matters

This would make the Azure DevOps integration much more useful for starting work directly from the issue/task, without manual context copying.

### Repro steps

1. Open Azure DevOps canvas.

2. Open a work item.

3. Observe the title and description are visible.

4. Try to start implementation from that item.

5. The session does not receive the work item context automatically.

### Notes

This should mirror the existing **Fix** experience available for pull request comments, but for Azure DevOps work items.

Start by comparing the existing Fix flow for pull request comments with the Azure DevOps canvas work-item view described here. Verify that a one-click Fix or Implement action transfers the work item title and description into the active session, and that the flow works from an opened work item.

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