docs(js): Clarify docs on Next.js tracing setup

docs/platforms/javascript/guides/nextjs/manual-setup.mdx

@@ -87,7 +87,13 @@ export default withSentryConfig(nextConfig, {
 
 ### Initialize Sentry Client-Side and Server-Side SDKs
 
-Create three files in your application's root directory: `sentry.server.config.(js|ts)`, `sentry.edge.config.(js|ts)`, and `instrumentation-client.(js|ts)`. Add the following initialization code into each respective file:
+Create three files in your application's root directory:
+- `sentry.server.config.(js|ts)`
+- `sentry.edge.config.(js|ts)`
+- `instrumentation-client.(js|ts)`
+  - If you previously had a file called `sentry.client.config.(js|ts)`, you can safely rename this to `instrumentation-client.(js|ts)` for all Next.js versions.
+
+Add the following initialization code into each respective file:
 
 <Alert level="info" title="Note">
   These files run in different environments (browser, server, edge) and are
@@ -112,8 +118,8 @@ Sentry.init({
   // https://docs.sentry.io/platforms/javascript/configuration/options/#traces-sample-rate
   tracesSampleRate: 1.0,
   // ___PRODUCT_OPTION_END___ performance
-  // Replay may only be enabled for the client-side
   // ___PRODUCT_OPTION_START___ session-replay
+  // Replay may only be enabled for the client-side
   integrations: [Sentry.replayIntegration()],
 
   // Capture Replay for 10% of all sessions,
@@ -188,10 +194,8 @@ Sentry.init({
 });
 ```
 
-<Alert level="success" title="Tip">
-  Include your [Data Source Name](/concepts/key-terms/dsn-explainer/) (DSN)
-  directly in these files, or use a _public_ environment variable like
-  `NEXT_PUBLIC_SENTRY_DSN`.
+<Alert title="Tip">
+  Include your DSN directly in these files, or use a _public_ environment variable like `NEXT_PUBLIC_SENTRY_DSN`.
 </Alert>
 
 ### Register Sentry Server-Side SDK Initialization
@@ -210,12 +214,6 @@ export async function register() {
 }
 ```
 
-<Alert level="warning" title="Next.js version <15 only">
-  You need to enable the instrumentation hook by setting the
-  `experimental.instrumentationHook` to `true` in your `next.config.(js|mjs)`
-  file.
-</Alert>
-
 <Expandable title="Opt out of Sentry SDK bundling on client- or server-side.">
   If you want the Sentry SDK to be available on the server side and not on the
   client side, simply delete `instrumentation-client.(js|ts)`. This will prevent

platform-includes/performance/configure-sample-rate/javascript.nextjs.mdx

@@ -1,13 +1,45 @@
-Set `tracesSampleRate` in your config files, `instrumentation-client.js`, `sentry.server.config.js`, and `sentry.edge.config.js`:
+Set `tracesSampleRate` in your config files:
+- `sentry.server.config.js`
+- `sentry.edge.config.js`:
+- `instrumentation-client.js`
+  - If you previously had a file called `sentry.client.config.(js|ts)`, you can safely rename this to `instrumentation-client.(js|ts)` for all Next.js versions.
 
-```javascript
+```javascript {tabTitle:Client} {filename:instrumentation-client.(js|ts)}
 import * as Sentry from "@sentry/nextjs";
 
 Sentry.init({
   dsn: "___PUBLIC_DSN___",
+  // We recommend adjusting this value in production, or using `tracesSampler`
+  // for finer control
+  tracesSampleRate: 1.0,
+  // ... rest of your config
+});
+
+// This export will instrument router navigations, and is only relevant if you enable tracing.
+// `captureRouterTransitionStart` is available from SDK version 9.12.0 onwards
+export const onRouterTransitionStart = Sentry.captureRouterTransitionStart;
+```
+
+```javascript {tabTitle:Server} {filename:sentry.server.config.(js|ts)}
+import * as Sentry from "@sentry/nextjs";
 
+Sentry.init({
+  dsn: "___PUBLIC_DSN___",
   // We recommend adjusting this value in production, or using `tracesSampler`
   // for finer control
   tracesSampleRate: 1.0,
+  // ... rest of your config
 });
 ```
+
+```javascript {tabTitle:Edge} {filename:sentry.edge.config.(js|ts)}
+import * as Sentry from "@sentry/nextjs";
+
+Sentry.init({
+  dsn: "___PUBLIC_DSN___",
+  // We recommend adjusting this value in production, or using `tracesSampler`
+  // for finer control
+  tracesSampleRate: 1.0,
+  // ... rest of your config
+});
+```