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/index.mdx

@@ -0,0 +1,70 @@
+---
+title: UI Components Overview
+sidebar_label: Overview
+sidebar_position: 0
+---
+
+<!--
+    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 { ComponentIndex } from '@site/src/components/ui-components';
+import componentData from '@site/static/data/components.json';
+
+# UI Components
+
+<ComponentIndex data={componentData} />
+
+---
+
+## Design System
+
+A design system is a complete set of standards intended to manage design at scale using reusable components and patterns.
+
+The Superset Design System uses [Atomic Design](https://bradfrost.com/blog/post/atomic-web-design/) principles with adapted terminology:
+
+| Atomic Design | Atoms | Molecules | Organisms | Templates | Pages / Screens |
+|---|:---:|:---:|:---:|:---:|:---:|
+| **Superset Design** | Foundations | Components | Patterns | Templates | Features |
+
+<img src="/img/atomic-design.png" alt="Atoms = Foundations, Molecules = Components, Organisms = Patterns, Templates = Templates, Pages / Screens = Features" style={{maxWidth: '100%'}} />
+
+## Usage
+
+All components are exported from `@superset-ui/core/components`:
+
+```tsx
+import { Button, Modal, Select } from '@superset-ui/core/components';
+```
+
+## Contributing
+
+This documentation is auto-generated from Storybook stories. To add or update component documentation:
+
+1. Create or update the component's `.stories.tsx` file
+2. Add a descriptive `title` and `description` in the story meta
+3. Export an interactive story with `args` for configurable props
+4. Run `yarn generate:superset-components` in the `docs/` directory
+
+:::info Work in Progress
+This component library is actively being documented. See the [Components TODO](./TODO) page for a list of components awaiting documentation.
+:::
+
+---
+
+*Auto-generated from Storybook stories in the [Design System/Introduction](https://github.com/apache/superset/blob/master/superset-frontend/packages/superset-ui-core/src/components/DesignSystem.stories.tsx) story.*