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

docs/nix/flake-module.nix

@@ -29,7 +29,10 @@
       # Frontmatter for clanModules
       clanModulesFrontmatter =
         let
-          docs = pkgs.nixosOptionsDoc { options = self.clanLib.modules.frontmatterOptions; };
+          docs = pkgs.nixosOptionsDoc {
+            options = self.clanLib.modules.frontmatterOptions;
+            transformOptions = self.clanLib.docs.stripStorePathsFromDeclarations;
+          };
         in
         docs.optionsJSON;