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/api/schemas/datasetrestapi-get.schema.mdx

@@ -0,0 +1,31 @@
+---
+id: datasetrestapi-get
+title: "DatasetRestApi.get"
+description: ""
+sidebar_label: "DatasetRestApi.get"
+hide_title: true
+hide_table_of_contents: true
+schema: true
+sample: {"always_filter_main_dttm":true,"catalog":"string","changed_by":{"first_name":"string","last_name":"string"},"changed_on":"2024-07-29T15:51:28.071Z","columns":{"advanced_data_type":"string","changed_on":"2024-07-29T15:51:28.071Z","column_name":"string","created_on":"2024-07-29T15:51:28.071Z","description":"string","expression":"string","extra":"string","filterable":true,"groupby":true,"id":0,"is_active":true,"is_dttm":true,"python_date_format":"string","type":"string","uuid":"3fa85f64-5717-4562-b3fc-2c963f66afa6","verbose_name":"string"},"created_by":{"first_name":"string","last_name":"string"},"created_on":"2024-07-29T15:51:28.071Z","currency_code_column":"string","database":{"database_name":"string","id":0,"uuid":"3fa85f64-5717-4562-b3fc-2c963f66afa6"},"default_endpoint":"string","description":"string","extra":"string","fetch_values_predicate":"string","filter_select_enabled":true,"id":0,"is_managed_externally":true,"is_sqllab_view":true,"main_dttm_col":"string","metrics":{"changed_on":"2024-07-29T15:51:28.071Z","created_on":"2024-07-29T15:51:28.071Z","d3format":"string","description":"string","expression":"string","extra":"string","id":0,"metric_name":"string","metric_type":"string","uuid":"3fa85f64-5717-4562-b3fc-2c963f66afa6","verbose_name":"string","warning_text":"string"},"normalize_columns":true,"offset":0,"owners":{"first_name":"string","id":0,"last_name":"string"},"schema":"string","sql":"string","table_name":"string","template_params":"string","uuid":"3fa85f64-5717-4562-b3fc-2c963f66afa6"}
+custom_edit_url: null
+---
+
+import Schema from "@theme/Schema";
+import Heading from "@theme/Heading";
+
+<Heading
+  as={"h1"}
+  className={"openapi__heading"}
+  children={"DatasetRestApi.get"}
+>
+</Heading>
+
+
+
+
+
+<Schema
+  {...require("./datasetrestapi-get.Schema.json")}
+>
+
+</Schema>