Remove `provides.itself` references and change `.provides.` -> `._.` in readme (#13)

README.md

···
       nixos  = {};
       darwin = {};
 
-      provides.emulation = { aspect, ... }: {
+      _.emulation = { aspect, ... }: {
         nixos = {};
 
         _.nes.nixos = {};
···
 
 A provider can be either a static aspect object or a function that dynamically returns one. This mechanism enables sophisticated dependency chains, conditional logic, and parameterization.
 
-#### The Default Provider: `provides.itself`
-
-Every aspect automatically has a default provider called `itself`, located at `<aspect>.provides.itself`. This provider simply returns the aspect itself.
+#### Default Provider (`__functor`)
 
-The `with aspects; [ bar baz ]` syntax is a convenient shorthand that relies on this default:
+Each aspect is itself a provider via its hidden option `__functor` (see `nix/types.nix`). You can include aspects directly.
 
 ```nix
 # A 'foo' aspect that depends on 'bar' and 'baz' aspects.
 flake.aspects = { aspects, ... }: {
   foo.includes = with aspects; [ bar baz ];
-  # This is equivalent to:
-  # foo.includes = [ aspects.bar.provides.itself aspects.baz.provides.itself ];
 }
 ```
 
···
 In this example, the `kde-desktop` aspect defines a custom `karousel` provider that only returns a module if certain conditions are met:
 
 ```nix
-flake.aspects.kde-desktop.provides.karousel = { aspect-chain, class }:
+flake.aspects.kde-desktop._.karousel = { aspect-chain, class }:
   if someCondition aspect-chain && class == "nixos" then { nixos = { ... }; } else { };
 ```
 
···
 
 ```nix
 flake.aspects = { aspects, ... }: {
-  home-server.includes = [ aspects.kde-desktop.provides.karousel ];
+  home-server.includes = [ aspects.kde-desktop._.karousel ];
 }
 ```
 
···
 flake.aspects = { aspects, ... }: {
   system = {
     nixos.system.stateVersion = "25.11";
-    provides.user = userName: {
+    _.user = userName: {
       darwin.system.primaryUser = userName;
       nixos.users.${userName}.isNormalUser = true;
     };
···
 
   home-server.includes = [
     aspects.system
-    (aspects.system.provides.user "bob")
+    (aspects.system._.user "bob")
   ];
 }
 ```