FEATURE | ChatPrompt V2: Historical turn view and revert functionality

📋 Description

Add ability to view and revert to historical conversation turns in ChatPrompt V2 extraction panel.

🎯 Context

When user selects a non-final turn in conversation history:

• Currently shows intermediate result with grayed overlay
• Need to add action buttons for viewing/reverting

✅ Requirements

UI Changes (ExtractionDetailView)

Add 3 buttons in top-right corner when viewing historical turn:

1. 👁️ View This Result

• Removes gray overlay
• Hides buttons 1) and 2)
• Keeps only button 3) visible
• Read-only view of intermediate result

1. ⏪ Revert to This Result

• Calls new backend API to delete all turns with index > selected turn
• Refreshes entire thread state after successful deletion
• Updates conversation bubbles and result display

1. ⏭️ View Final Result

• Switches back to the latest/final turn
• Restores normal view (no overlay, no special buttons)

Backend API (new endpoint needed)

DELETE /api/chat/threads/{threadId}/turns?afterIndex={turnIndex}

• Deletes all turns with index greater than specified
• Returns updated thread state

State Management

• Track IsViewingHistoricalTurn in ViewModel
• Track SelectedHistoricalTurnIndex
• Handle overlay visibility based on state

🎨 UI Mockup

┌─────────────────────────────────────────────┐
│ [View This] [Revert to This] [View Final] ▢ │  <- new buttons
├─────────────────────────────────────────────┤
│ ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░ │
│ ░░░ Historical result (grayed overlay) ░░░░ │
│ ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░ │
└─────────────────────────────────────────────┘

📁 Files to Modify

• src/ViewModels/Panel/ChatPrompts/ExtractionDetailViewModel.cs - state & commands
• src/SVIViews/Panel/ChatPrompts/ExtractionDetailView.xaml - buttons UI
• src/AppraisalData/Abstractions/IChatServiceProvider.cs - new method
• src/AppraisalData/Logic/ChatServiceProvider.cs - API call implementation
• Backend: new endpoint for turn deletion

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~ Lili