[WIP] Migrate to modern supported parser XParsec or SharpParser.Core

[Copilot]

• Inspect repository to locate parser implementation and current FParsec usage
• Define minimal migration plan to move parser dependency to a maintained parser library
• Run baseline targeted build/tests for parser-related projects before changes
• Migrate parser code from FParsec API usage to the selected maintained parser API (XParsec)
• Update package references to remove FParsec and use XParsec where needed
• Add or adjust focused parser tests only if required by migration behavior differences
• Run targeted parser tests/build and fix any regressions
• Run final validation (including parallel_validation) and summarize results