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

Snapshots all four versioned Docusaurus sections at v6.1.0, cut from
master after the version-cutting tooling (#39837), broken-internal-
links fix (#40102), and user_docs rename (#40171) all landed. With
the rename in place, all four sections now produce parallel-named
files at the docs/ root (no more bare `versioned_docs/` outlier).

Versioning behavior: lastVersion stays at current for every section,
so the canonical URLs (/user-docs/..., /admin-docs/...,
/developer-docs/..., /components/...) continue to render content
from master. The current version is consistently labeled "Next"
with an unreleased banner, and 6.1.0 is a historical pin accessible
only via its explicit version segment.

Component playground: previously disabled: true in versions-config.json,
now enabled and versioned.

Snapshot includes:
- All MDX content for the four sections.
- Auto-gen captured fresh: 74 database pages (engine spec metadata),
  ~1,800 API reference files (openapi.json), 59 component pages
  (Storybook stories).
- Data imports frozen at cut time into snapshot-local _versioned_data/
  dirs:
    user_docs_versioned_docs/version-6.1.0/_versioned_data/src/data/databases.json
      (canonical 80-database diagnostics from master, preserved by the
      generator's input-hash cache)
    admin_docs_versioned_docs/version-6.1.0/_versioned_data/data/countries.json
    admin_docs_versioned_docs/version-6.1.0/_versioned_data/static/feature-flags.json
    developer_docs_versioned_docs/version-6.1.0/_versioned_data/static/data/components.json
- Import paths in deeply-nested files rewritten so they still resolve
  from one directory deeper inside the snapshot.
- developer_docs/extensions/overview.md snapshot has the FIXED
  ./mcp.md form (from #40102), so the SPA-nav 404 isn't baked into
  the 6.1.0 version.

Verified via full yarn build: exit 0, no broken links surfaced by
onBrokenLinks: throw.

docs/components_versioned_docs/version-6.1.0/chart-components/bar-chart.md

@@ -0,0 +1,105 @@
+<!--
+    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: Bar Chart
+sidebar_position: 1
+---
+
+# Bar Chart Component
+
+The Bar Chart component is used to visualize categorical data with rectangular bars.
+
+## Props
+
+| Prop | Type | Default | Description |
+|------|------|---------|-------------|
+| `data` | `array` | `[]` | Array of data objects to visualize |
+| `width` | `number` | `800` | Width of the chart in pixels |
+| `height` | `number` | `600` | Height of the chart in pixels |
+| `xField` | `string` | - | Field name for x-axis values |
+| `yField` | `string` | - | Field name for y-axis values |
+| `colorField` | `string` | - | Field name for color encoding |
+| `colorScheme` | `string` | `'supersetColors'` | Color scheme to use |
+| `showLegend` | `boolean` | `true` | Whether to show the legend |
+| `showGrid` | `boolean` | `true` | Whether to show grid lines |
+| `labelPosition` | `string` | `'top'` | Position of bar labels: 'top', 'middle', 'bottom' |
+
+## Examples
+
+### Basic Bar Chart
+
+```jsx
+import { BarChart } from '@superset-ui/chart-components';
+
+const data = [
+  { category: 'A', value: 10 },
+  { category: 'B', value: 20 },
+  { category: 'C', value: 15 },
+  { category: 'D', value: 25 },
+];
+
+function Example() {
+  return (
+    <BarChart
+      data={data}
+      width={800}
+      height={400}
+      xField="category"
+      yField="value"
+      colorScheme="supersetColors"
+    />
+  );
+}
+```
+
+### Grouped Bar Chart
+
+```jsx
+import { BarChart } from '@superset-ui/chart-components';
+
+const data = [
+  { category: 'A', group: 'Group 1', value: 10 },
+  { category: 'A', group: 'Group 2', value: 15 },
+  { category: 'B', group: 'Group 1', value: 20 },
+  { category: 'B', group: 'Group 2', value: 25 },
+  { category: 'C', group: 'Group 1', value: 15 },
+  { category: 'C', group: 'Group 2', value: 10 },
+];
+
+function Example() {
+  return (
+    <BarChart
+      data={data}
+      width={800}
+      height={400}
+      xField="category"
+      yField="value"
+      colorField="group"
+      colorScheme="supersetColors"
+    />
+  );
+}
+```
+
+## Best Practices
+
+- Use bar charts when comparing quantities across categories
+- Sort bars by value for better readability, unless there's a natural order to the categories
+- Use consistent colors for the same categories across different charts
+- Consider using horizontal bar charts when category labels are long