docs: cut 6.1.0 versions for docs, admin_docs, developer_docs, components

- Snapshot all four versioned docs sections at v6.1.0; master continues to
  serve as "Next" (lastVersion: current, banner: unreleased) so editing
  master keeps updating the canonical URLs
- Enable the previously-disabled components plugin and version it
- Rename stale "developer_portal" references to "developer_docs" across
  package.json scripts, manage-versions.mjs, theme files (DocVersionBadge,
  DocVersionBanner), DOCS_CLAUDE.md, and README.md (URL backward-compat
  redirect /developer_portal/* preserved)
- Add admin_docs version scripts; drop dead "tutorials" plugin id from
  the version badge
- Generalize fixVersionedImports in manage-versions.mjs to walk every
  section's snapshot and rewrite ../../src/ and ../../data/ imports,
  catching admin_docs and components files that previous version cuts
  would have broken
- Remove orphan files: developer_portal_versions.json,
  tutorials_versions.json, and stray empty versions.json files inside
  components/ and developer_docs/ content directories

docs/developer_docs_versioned_docs/version-6.1.0/components/extension/alert.mdx

@@ -0,0 +1,119 @@
+---
+title: Alert
+sidebar_label: Alert
+---
+
+<!--
+    Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements.  See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.  The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing,
+    software distributed under the License is distributed on an
+    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+    KIND, either express or implied.  See the License for the
+    specific language governing permissions and limitations
+    under the License.
+-->
+
+import { StoryWithControls } from '../../../src/components/StorybookWrapper';
+
+# Alert
+
+Alert component for displaying important messages to users. Wraps Ant Design Alert with sensible defaults and improved accessibility.
+
+## Live Example
+
+<StoryWithControls
+  component="Alert"
+  props={{
+  closable: true,
+  type: "info",
+  message: "This is a sample alert message.",
+  description: "Sample description for additional context.",
+  showIcon: true
+}}
+  controls={[
+  {
+    name: "closable",
+    label: "Closable",
+    type: "boolean",
+    description: "Whether the Alert can be closed with a close button."
+  },
+  {
+    name: "type",
+    label: "Type",
+    type: "select",
+    options: [
+      "info",
+      "error",
+      "warning",
+      "success"
+    ],
+    description: "Type of the alert (e.g., info, error, warning, success)."
+  },
+  {
+    name: "message",
+    label: "Message",
+    type: "text"
+  },
+  {
+    name: "description",
+    label: "Description",
+    type: "text"
+  },
+  {
+    name: "showIcon",
+    label: "Show Icon",
+    type: "boolean",
+    description: "Whether to display an icon in the Alert."
+  }
+]}
+/>
+
+## Try It
+
+Edit the code below to experiment with the component:
+
+```tsx live
+function Demo() {
+  return (
+    <Alert
+      closable
+      type="info"
+      message="This is a sample alert message."
+      description="Sample description for additional context."
+      showIcon
+    />
+  );
+}
+```
+
+## Props
+
+| Prop | Type | Default | Description |
+|------|------|---------|-------------|
+| `closable` | `boolean` | `true` | Whether the Alert can be closed with a close button. |
+| `type` | `string` | `"info"` | Type of the alert (e.g., info, error, warning, success). |
+| `message` | `string` | `"This is a sample alert message."` | - |
+| `description` | `string` | `"Sample description for additional context."` | - |
+| `showIcon` | `boolean` | `true` | Whether to display an icon in the Alert. |
+
+## Import
+
+```tsx
+import { Alert } from 'packages/superset-core/src/ui/components/Alert';
+```
+
+---
+
+:::tip[Improve this page]
+This documentation is auto-generated from the component's Storybook story.
+Help improve it by [editing the story file](https://github.com/apache/superset/edit/master/superset-frontend/packages/superset-core/src/ui/components/Alert/Alert.stories.tsx).
+:::

docs/developer_docs_versioned_docs/version-6.1.0/components/extension/index.mdx

@@ -0,0 +1,32 @@
+---
+title: Extension Components
+sidebar_label: Extension Components
+sidebar_position: 1
+---
+
+<!--
+    Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements.  See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.  The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing,
+    software distributed under the License is distributed on an
+    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+    KIND, either express or implied.  See the License for the
+    specific language governing permissions and limitations
+    under the License.
+-->
+
+# Extension Components
+
+1 components available in this category.
+
+## Components
+
+- [Alert](./alert)