docs(sdk): Add runtime to SDK interface

develop-docs/sdk/data-model/event-payloads/sdk.mdx

@@ -69,6 +69,16 @@ activated integrations. Each package consists of a `name` in the format
 `identifier` should be a checkout link and the `version` should be a Git
 reference (branch, tag or SHA).
 
+`runtime`
+
+: _Optional_. A string to identify the runtime environment when it's not obvious from
+the SDK name alone. This field is particularly valuable in Meta-Frameworks (like Next.js,
+Nuxt or React Router) to distinguish between frontend and backend parts.
+Displaying this field in issue details allows developers to quickly determine where an error
+occurred without examining the full error context. The following strings are available:
+  - `"Frontend"` - Code running in the browser
+  - `"Backend"` - Code running on servers, web workers, or edge runtimes
+
 ## Example
 
 The following example illustrates the SDK part of the <Link to="/sdk/data-model/event-payloads/">event payload</Link> and omits other
@@ -94,3 +104,27 @@ attributes for simplicity.
   }
 }
 ```
+
+The following example shows the usage of the `runtime` label for Meta-Frameworks:
+
+```json
+{
+  "sdk": {
+    "name": "sentry.javascript.nuxt",
+    "version": "9.10.0",
+    "integrations": ["BrowserTracing", "Vue"],
+    "runtime": "Frontend",
+    "packages": [
+      {
+        "name": "npm:@sentry/nuxt",
+        "version": "9.10.0"
+      },
+      {
+        "name": "npm:@sentry/vue",
+        "version": "9.10.0"
+      }
+    ]
+  },
+}
+```
+