fix(release): Stage Claude plugin manifests explicitly

Replace the derived .claude-plugin directory entry with the concrete\nplugin manifest files so release:prepare can git-add them without\ntripping over the ignore rule for the directory itself.\n\nAdd matching test updates for the workflow contract.

tools/scripts/tests/automation_workflows.test.js

@@ -62,7 +62,8 @@ for (const filePath of [
   "apps/web-app/public/skills.json.backup",
   "data/plugin-compatibility.json",
   ".agents/plugins/",
-  ".claude-plugin/",
+  ".claude-plugin/plugin.json",
+  ".claude-plugin/marketplace.json",
   "plugins/",
 ]) {
   assert.ok(

tools/scripts/tests/workflow_contracts.test.js

@@ -19,7 +19,8 @@ const contract = {
     "data/plugin-compatibility.json",
     "data/aliases.json",
     ".agents/plugins/",
-    ".claude-plugin/",
+    ".claude-plugin/plugin.json",
+    ".claude-plugin/marketplace.json",
     "plugins/",
   ],
   mixedFiles: ["README.md"],