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/developer_docs_versioned_docs/version-6.1.0/sidebars.js

@@ -0,0 +1,84 @@
+/**
+ * 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.
+ */
+
+module.exports = {
+  developerPortalSidebar: [
+    'index',
+    {
+      type: 'category',
+      label: 'Contributing',
+      collapsed: true,
+      items: [
+        'contributing/overview',
+        'guidelines/design-guidelines',
+        'guidelines/frontend-style-guidelines',
+        'guidelines/backend-style-guidelines',
+      ],
+    },
+    {
+      type: 'category',
+      label: 'Extensions',
+      collapsed: true,
+      items: [
+        'extensions/overview',
+        'extensions/quick-start',
+        'extensions/architecture',
+        'extensions/dependencies',
+        'extensions/contribution-types',
+        {
+          type: 'category',
+          label: 'Extension Points',
+          collapsed: true,
+          items: [
+            'extensions/extension-points/sqllab',
+          ],
+        },
+        'extensions/development',
+        'extensions/deployment',
+        'extensions/mcp',
+        'extensions/security',
+        'extensions/tasks',
+        'extensions/registry',
+      ],
+    },
+    {
+      type: 'category',
+      label: 'Testing',
+      collapsed: true,
+      items: [
+        'testing/overview',
+      ],
+    },
+    {
+      type: 'category',
+      label: 'UI Components',
+      collapsed: true,
+      link: {
+        type: 'doc',
+        id: 'components/index',
+      },
+      items: [
+        {
+          type: 'autogenerated',
+          dirName: 'components',
+        },
+      ],
+    },
+  ],
+};