refactor: move docs transformOptions to clanLib to reduce rebuilds

- Add clanLib.docs.stripStorePathsFromDeclarations to deduplicate code
- Update all documentation generation to use the shared function
- This strips store paths from option declarations to prevent options.json
  from rebuilding when only store paths change but content remains the same
- Reduces unnecessary documentation rebuilds when making unrelated changes

lib/modules/eval-docs.nix

@@ -9,9 +9,11 @@ let
       clan-core.modules.clan.default
     ];
   };
+
   evalDocs = pkgs.nixosOptionsDoc {
     options = eval.options;
     warningsAreErrors = false;
+    transformOptions = clan-core.clanLib.docs.stripStorePathsFromDeclarations;
   };
 in
 {