[Feature]: Round-trip tests for editing and export  #85

What type of issue is this?

• Bug report
• Feature request

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the reqifviewer
• I have searched open and closed issues to ensure it has not already been reported

Description

Acceptance criteria

• For each sample: load, apply a scripted set of edits, export, re-load; the result is schema-valid, contains exactly the intended changes, and keeps attachments.

Steps to Reproduce

NA

System Configuration

• reqifviewer version: 6.1.0 (development, with [Refactor] Blazor Blueprint app shell and Blazor Web App hosting #56)
• Environment (Operating system, version and so on): Windows 11, Chrome
• .NET Framework version: .NET 10
• Additional information: Plan item E-07 of the viewer improvement plan. Size: M. Depends on: [Feature]: Review changes and export a new version  #84.