chore: reorganize docs and remove testing infrastructure

 - Organize docs into logical subfolders (development/, testing/, grant/)
 - Keep essential user-facing docs in root (API.md, BENCHMARKS.md, etc.)
 - Remove server/deployment infrastructure (not part of SDK)
 - Remove personal integration files (Fabstir, webxdc examples)
 - Clean up testing scripts and obsolete documentation

 This prepares the repository for upstream PR by focusing on SDK code,
 tests, and user-facing documentation.

Author: Developer