docs: clarify close hook availability across preset types

Note that the close hook only fires on long-running server presets
(node, bun, deno) and not in serverless/edge environments. Guide plugin
authors toward the response hook or waitUntil for per-request cleanup
that works across all presets.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: wadefletch

docs/1.docs/50.plugins.md

@@ -54,10 +54,10 @@ export default definePlugin((nitro) => {
 
 ### Available hooks
 
-- `"request", (event) => {}` - Called when a request is received.
-- `"error", (error, { event? }) => {}` - Called when an error is captured.
-- `"response", (response, event) => {}` - Called when a response is sent.
-- `"close", () => {}` - Called when the server receives a shutdown signal (`SIGTERM` or `SIGINT`).
+- `"request", (event) => {}` - Called when a request is received. Available in all presets.
+- `"error", (error, { event? }) => {}` - Called when an error is captured. Available in all presets.
+- `"response", (response, event) => {}` - Called when a response is sent. Available in all presets.
+- `"close", () => {}` - Called when the server receives a shutdown signal (`SIGTERM` or `SIGINT`). Only available in long-running server presets (Node.js, Bun, Deno). Not called in serverless or edge environments.
 
 ## Examples
 
@@ -77,7 +77,7 @@ export default definePlugin((nitro) => {
 
 ### Graceful shutdown
 
-When the server receives a shutdown signal (`SIGTERM` or `SIGINT`), the `close` hook is called, allowing plugins to run async cleanup before the process exits. This is useful for flushing telemetry, draining database connections, stopping job queues, and other teardown tasks.
+On long-running server presets (`node-server`, `node-cluster`, `bun`, `deno-server`), the `close` hook fires when the process receives `SIGTERM` or `SIGINT`, allowing plugins to run async cleanup before exit.
 
 ```ts
 import { definePlugin } from "nitro";
@@ -90,6 +90,20 @@ export default definePlugin((nitro) => {
 })
 ```
 
+Serverless and edge runtimes (Cloudflare Workers, AWS Lambda, Vercel, Netlify, Deno Deploy) do not have a shutdown signal–the platform terminates the execution context without notice. The `close` hook will not fire in these environments.
+
+For per-request cleanup that works across all presets, use the `"response"` hook or `request.waitUntil()` instead:
+
+```ts
+import { definePlugin } from "nitro";
+
+export default definePlugin((nitro) => {
+  nitro.hooks.hook("response", async (response, event) => {
+    await flushRequestTelemetry(event);
+  });
+})
+```
+
 ### Request and response lifecycle
 
 You can use plugins to register a hook that can run on request lifecycle: