refactor: remove deployment.json and use direct selectors

- Remove deployment.json file generation from outputs.nix
- Add throw for deprecated deployment.file usage with upgrade instructions
- Remove vars data from deployment.data
- Update Machine class to use direct select() calls instead of deployment property
- Update all deployment property accesses to use direct selectors
- Add precaching for frequently accessed values in update.py:
  - Module paths for facts and vars
  - Deployment settings (requireExplicitUpdate, nixosMobileWorkaround)
  - Services and generators data
  - Secret upload locations
- This removes unnecessary JSON serialization and makes the code more composable

nixosModules/clanCore/outputs.nix

@@ -1,7 +1,6 @@
 {
   config,
   lib,
-  pkgs,
   ...
 }:
 {
@@ -24,6 +23,14 @@
           description = ''
             the location of the deployment.json file
           '';
+          default = throw ''
+            deployment.json file generation has been removed in favor of direct selectors.
+
+            Please upgrade your clan-cli to the latest version.
+
+            The deployment data is now accessed directly from the configuration
+            instead of being written to a separate JSON file.
+          '';
         };
         deployment.buildHost = lib.mkOption {
           type = lib.types.nullOr lib.types.str;
@@ -83,8 +90,5 @@
       inherit (config.clan.core.deployment) requireExplicitUpdate;
       inherit (config.system.clan.deployment) nixosMobileWorkaround;
     };
-    system.clan.deployment.file = pkgs.writeText "deployment.json" (
-      builtins.toJSON config.system.clan.deployment.data
-    );
   };
 }