Feature/docs

[SolidArcSoftware]

Summary

Adds the initial DocFX documentation site for DataArc.EntityFrameworkCore.

The documentation covers the core execution model, including:

• execution contexts;
• query pipelines;
• command pipelines;
• bulk and parallel operations;
• transactional workflows;
• structured execution results;
• database and script generation;
• compatibility;
• trial and licensing information.

This change also adds the GitHub Pages workflow required to build and publish the generated DocFX site from the docs folder.

Validation

• Documentation builds successfully with DocFX.
• Existing solution restore and build remain unchanged.
• Generated _site output is excluded from source control.