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/components_versioned_docs/version-6.1.0/layout-components/grid.md

@@ -0,0 +1,113 @@
+<!--
+    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.
+-->
+---
+title: Grid
+sidebar_position: 1
+---
+
+# Grid Component
+
+The Grid component provides a flexible layout system for arranging content in rows and columns.
+
+## Props
+
+| Prop | Type | Default | Description |
+|------|------|---------|-------------|
+| `gutter` | `number` or `[number, number]` | `0` | Grid spacing between items, can be a single number or [horizontal, vertical] |
+| `columns` | `number` | `12` | Number of columns in the grid |
+| `justify` | `string` | `'start'` | Horizontal alignment: 'start', 'center', 'end', 'space-between', 'space-around' |
+| `align` | `string` | `'top'` | Vertical alignment: 'top', 'middle', 'bottom' |
+| `wrap` | `boolean` | `true` | Whether to wrap items when they overflow |
+
+### Row Props
+
+| Prop | Type | Default | Description |
+|------|------|---------|-------------|
+| `gutter` | `number` or `[number, number]` | `0` | Spacing between items in the row |
+| `justify` | `string` | `'start'` | Horizontal alignment for this row |
+| `align` | `string` | `'top'` | Vertical alignment for this row |
+
+### Col Props
+
+| Prop | Type | Default | Description |
+|------|------|---------|-------------|
+| `span` | `number` | - | Number of columns the grid item spans |
+| `offset` | `number` | `0` | Number of columns the grid item is offset |
+| `xs`, `sm`, `md`, `lg`, `xl` | `number` or `object` | - | Responsive props for different screen sizes |
+
+## Examples
+
+### Basic Grid
+
+```jsx
+import { Grid, Row, Col } from '@superset-ui/core';
+
+function Example() {
+  return (
+    <Grid>
+      <Row gutter={16}>
+        <Col span={8}>
+          <div>Column 1</div>
+        </Col>
+        <Col span={8}>
+          <div>Column 2</div>
+        </Col>
+        <Col span={8}>
+          <div>Column 3</div>
+        </Col>
+      </Row>
+    </Grid>
+  );
+}
+```
+
+### Responsive Grid
+
+```jsx
+import { Grid, Row, Col } from '@superset-ui/core';
+
+function Example() {
+  return (
+    <Grid>
+      <Row gutter={[16, 24]}>
+        <Col xs={24} sm={12} md={8} lg={6}>
+          <div>Responsive Column 1</div>
+        </Col>
+        <Col xs={24} sm={12} md={8} lg={6}>
+          <div>Responsive Column 2</div>
+        </Col>
+        <Col xs={24} sm={12} md={8} lg={6}>
+          <div>Responsive Column 3</div>
+        </Col>
+        <Col xs={24} sm={12} md={8} lg={6}>
+          <div>Responsive Column 4</div>
+        </Col>
+      </Row>
+    </Grid>
+  );
+}
+```
+
+## Best Practices
+
+- Use the Grid system for complex layouts that need to be responsive
+- Specify column widths for different screen sizes to ensure proper responsive behavior
+- Use gutters to create appropriate spacing between grid items
+- Keep the grid structure consistent throughout your application
+- Consider using the grid system for dashboard layouts to ensure consistent spacing and alignment