modules: move clan docs into clan-module

modules/clan/eval-docs.nix

@@ -0,0 +1,23 @@
+{
+  pkgs,
+  lib,
+  clanModule,
+  clanLib,
+}:
+let
+  eval = lib.evalModules {
+    modules = [
+      clanModule
+    ];
+  };
+
+  evalDocs = pkgs.nixosOptionsDoc {
+    options = eval.options;
+    warningsAreErrors = false;
+    transformOptions = clanLib.docs.stripStorePathsFromDeclarations;
+  };
+in
+{
+  inherit (evalDocs) optionsJSON optionsNix;
+  inherit eval;
+}

modules/clan/flake-module.nix

@@ -1,4 +1,26 @@
 { self, lib, ... }:
+let
+  clanModule = lib.modules.importApply ./default.nix { clan-core = self; };
+in
 {
-  flake.modules.clan.default = lib.modules.importApply ./default.nix { clan-core = self; };
+  flake.modules.clan.default = clanModule;
+  perSystem =
+    {
+      pkgs,
+      lib,
+      ...
+    }:
+    let
+      jsonDocs = import ./eval-docs.nix {
+        inherit
+          pkgs
+          lib
+          clanModule
+          ;
+        clanLib = self.clanLib;
+      };
+    in
+    {
+      legacyPackages.clan-options = jsonDocs.optionsJSON;
+    };
 }