Refactor documentation structure to separate Framework and Protocols

- Deleted the "Writing Plugins" guide from the documentation.
- Renamed "Developers" section to "Framework" for clarity on its focus.
- Updated protocol section titles for consistency:
  - "ObjectQL (Data Protocol)" to "Protocol: Data (ObjectQL)"
  - "ObjectUI (UI Protocol)" to "Protocol: UI (ObjectUI)"
  - "ObjectOS (System Protocol)" to "Protocol: System (ObjectOS)"
- Introduced dividers in the documentation structure for better navigation.
- Verified all links and updated navigation files accordingly.

Author: hotlong