Move Home Manager module defaults from a centralized `desktop-home-defaults.nix`
file into their respective `wisdom` slices. This change aligns with the
updated documentation regarding module ownership, where defaults live
with the option that owns them rather than in a shared defaults file.
Additionally, update `docs/conventions.md` to reflect this new pattern for
defining `mkEnableOption` defaults and move base git/encryption
configurations into the core `wisdom` module.
- Delete `modules/hosts/desktop-home-defaults.nix`
- Update `modules/wisdom/default.nix` to include shared git and package defaults
- Add `default = ...` to `mkEnableOption` in various `wisdom` modules
- Update `docs/conventions.md` with new HM slice guidelines
- Simplified the cursor package selection by removing the deprecated `cursor-agent` option and retaining only `cursor-cli`.
- Updated the activation script to remove the broken `cursor-agent` symlink, ensuring proper resolution to `cursor-cli`.
- Adjusted the configuration to reflect these changes in the Nix IDE tools integration.
Olivier