Update power rename doc

Author: khmyznikov

doc/devdocs/modules/powerrename.md

@@ -1,23 +1,100 @@
-#### [`dllmain.cpp`](/src/modules/powerrename/dll/dllmain.cpp)
-TODO
+# PowerRename
 
-#### [`PowerRenameExt.cpp`](/src/modules/powerrename/dll/PowerRenameExt.cpp)
-TODO
+PowerRename is a Windows shell extension that enables batch renaming of files using search and replace or regular expressions.
 
-#### [`Helpers.cpp`](/src/modules/powerrename/lib/Helpers.cpp)
-TODO
+## Overview
 
-#### [`PowerRenameItem.cpp`](/src/modules/powerrename/lib/PowerRenameItem.cpp)
-TODO
+PowerRename provides a powerful and flexible way to rename files in File Explorer. It is accessible through the Windows context menu and allows users to:
+- Preview changes before applying them
+- Use search and replace with regular expressions
+- Filter items by type (files or folders)
+- Apply case-sensitive or case-insensitive matching
+- Save and reuse recent search/replace patterns
 
-#### [`PowerRenameManager.cpp`](/src/modules/powerrename/lib/PowerRenameManager.cpp)
-TODO
+## Architecture
 
-#### [`PowerRenameRegEx.cpp`](/src/modules/powerrename/lib/PowerRenameRegEx.cpp)
-TODO
+PowerRename consists of multiple components:
+- Shell Extension DLL (context menu integration)
+- WinUI 3 UI application
+- Core renaming library
 
-#### [`Settings.cpp`](/src/modules/powerrename/lib/Settings.cpp)
-TODO
+### Technology Stack
+- C++/WinRT
+- WinUI 3
+- COM for shell integration
 
-#### [`trace.cpp`](/src/modules/powerrename/lib/trace.cpp)
-TODO
+## Context Menu Integration
+
+PowerRename integrates with the Windows context menu following the [PowerToys Context Menu Handlers](../common/context-menus.md) pattern. It uses a dual registration approach to ensure compatibility with both Windows 10 and Windows 11.
+
+### Registration Process
+
+The context menu registration entry point is in `PowerRenameExt/dllmain.cpp::enable`, which registers:
+- A traditional shell extension for Windows 10
+- A sparse MSIX package for Windows 11 context menus
+
+For more details on the implementation approach, see the [Dual Registration section](../common/context-menus.md#1-dual-registration-eg-imageresizer-powerrename) in the context menu documentation.
+
+## Code Components
+
+### [`dllmain.cpp`](/src/modules/powerrename/dll/dllmain.cpp)
+Contains the DLL entry point and module activation/deactivation code. The key function `RunPowerRename` is called when the context menu option is invoked, which launches the PowerRenameUI.
+
+### [`PowerRenameExt.cpp`](/src/modules/powerrename/dll/PowerRenameExt.cpp)
+Implements the shell extension COM interfaces required for context menu integration, including:
+- `IShellExtInit` for initialization 
+- `IContextMenu` for traditional context menu support
+- `IExplorerCommand` for Windows 11 context menu support
+
+### [`Helpers.cpp`](/src/modules/powerrename/lib/Helpers.cpp)
+Utility functions used throughout the PowerRename module, including file system operations and string manipulation.
+
+### [`PowerRenameItem.cpp`](/src/modules/powerrename/lib/PowerRenameItem.cpp)
+Represents a single item (file or folder) to be renamed. Tracks original and new names and maintains state.
+
+### [`PowerRenameManager.cpp`](/src/modules/powerrename/lib/PowerRenameManager.cpp)
+Manages the collection of items to be renamed and coordinates the rename operation.
+
+### [`PowerRenameRegEx.cpp`](/src/modules/powerrename/lib/PowerRenameRegEx.cpp)
+Implements the regular expression search and replace functionality used for renaming.
+
+### [`Settings.cpp`](/src/modules/powerrename/lib/Settings.cpp)
+Manages user preferences and settings for the PowerRename module.
+
+### [`trace.cpp`](/src/modules/powerrename/lib/trace.cpp)
+Implements telemetry and logging functionality.
+
+## UI Implementation
+
+PowerRename uses WinUI 3 for its user interface. The UI allows users to:
+- Enter search and replace patterns
+- Preview rename results in real-time
+- Access previous search/replace patterns via MRU (Most Recently Used) lists
+- Configure various options
+
+### Key UI Components
+
+- Search/Replace input fields with x:Bind to `SearchMRU`/`ReplaceMRU` collections
+- Preview list showing original and new filenames
+- Settings panel for configuring rename options
+- Event handling for `SearchReplaceChanged` to update the preview in real-time
+
+## Debugging
+
+### Debugging the Context Menu
+
+See the [Debugging Context Menu Handlers](../common/context-menus.md#debugging-context-menu-handlers) section for general guidance on debugging PowerToys context menu extensions.
+
+### Debugging the UI
+
+To debug the PowerRename UI:
+
+1. Add file paths manually in `\src\modules\powerrename\PowerRenameUILib\PowerRenameXAML\App.xaml.cpp`
+2. Set the PowerRenameUI project as the startup project
+3. Run in debug mode to test with the manually specified files
+
+### Common Issues
+
+- Context menu not appearing: Ensure the extension is properly registered and Explorer has been restarted
+- UI not launching: Check Event Viewer for errors related to WinUI 3 application activation
+- Rename operations failing: Verify file permissions and check for locked files