C# Word Add-in: Text Formatting

I need a Microsoft Word Add-in built with modern C# on the latest .NET framework that focuses exclusively on advanced text-formatting tools. The add-in should install seamlessly within Word for Windows, expose its features through a custom ribbon group, and run without external dependencies outside standard Office and .NET libraries.

Core scope
• Implement rich formatting commands—think custom style presets, fine-grained font controls, and one-click “clean & re-apply” logic—delivered through an intuitive UI that feels native to Word.
• Use the current Long-Term Support version of .NET; the solution must compile under Visual Studio and follow Microsoft’s recommended VSTO or Office Add-in patterns for C#.
• Persist user settings locally so preferred options survive across sessions, yet never write outside the user profile.
• Code must be well-structured, commented, and ready for future expansion (e.g., additional template features down the line).

Deliverables
1. Visual Studio solution (.sln) with all source code, assets, and a signed deployable installer (MSI or ClickOnce).
2. Step-by-step build and installation guide in Markdown.
3. Short demo document or screen-capture showing the formatting tools in action.
4. Two weeks of post-delivery bug fixes for issues reproducible on Word 2019 or Microsoft 365 (Windows desktop).

Acceptance criteria
• Add-in loads without security warnings on a clean machine.
• Ribbon buttons perform their designated formatting actions on selected text reliably.
• No unhandled exceptions appear in the Visual Studio diagnostics output when running in debug mode.
• All requirements above are met and confirmed during a live hand-over session.

If any clarification is needed on Word versions, UI mockups, or specific style behaviors, let me know early so we can lock requirements before you dive into coding.