Add page for supergraph build hibernation (#1061)

Author: imperfect-fourth

docs/reference/supergraph-build-hibernation.mdx

@@ -0,0 +1,44 @@
+---
+title: Supergraph build hibernation
+sidebar_label: Supergraph build hibernation
+sidebar_position: 20
+description:
+  "Understand when DDN hibernates unused supergraph builds and how to bring them back online from the CLI or console."
+keywords:
+  - supergraph builds
+  - hibernation
+  - hasura ddn
+  - cli
+  - console
+---
+
+import Thumbnail from "@site/src/components/Thumbnail";
+
+# Supergraph Build Hibernation
+
+## Overview
+
+Supergraph builds that remain unapplied and idle are automatically hibernated to conserve resources. Specifically:
+
+- Any unapplied build that is older than two days **and** has not received a request in the last two days is hibernated.
+- Hibernation pauses execution but preserves metadata and other build inputs so you can reactivate the build if needed.
+
+Once hibernated, a build must be explicitly reactivated before it can start
+serving traffic again. Until then, all requests will fail with 409 status code.
+
+## Reactivation
+
+You can bring a hibernated build back online through either the DDN CLI or the console.
+
+### Reactivate via CLI
+
+Run the `ddn supergraph build reactivate` command to reactivate the hibernated assets. Reference the full command options in the CLI docs:
+
+- [ddn supergraph build reactivate](/reference/cli/commands/ddn_supergraph_build_reactivate.mdx)
+
+### Reactivate via console
+
+1. Open your project on the Hasura console and navigate to the **Builds** page.
+2. Locate the hibernated build and select **Reactivate**. Confirm the action to immediately queue a rebuild and resume the associated API endpoint.
+
+<Thumbnail src="/img/supergraph-build-reactivation.png" alt="Reactivate a hibernated supergraph build" />