clean up defer docs

docs/async/defer.mdx

@@ -1,31 +1,34 @@
 ---
 title: defer
-description: Run an async function with deferred functions
+description: Defer work until an async function completes
 ---
 
 ### Usage
 
-The `_.defer` functions lets you run an async function, registering functions as you go
-that should be deferred until the async function completes, and then executed. This is
-really useful in scripts where failure up to or after a specific point will require some
-cleanup. It's a bit like a `finally` block.
+The `defer` function allows you to run an async function while registering cleanup functions that will execute after it completes. This is useful when you need to clean up resources regardless of whether the main function succeeds or fails, similar to a `finally` block.
 
-A hat tip to Swift's `defer` for the inspiration.
+The function passed to `defer` receives a `register` function as its argument. Use this to register cleanup work that should run after the main function finishes.
 
-The function passed to `_.defer` is called with a single `register` function argument that
-can be used to register the work you want to be called when the function completes. If your function throws an error and then a registered cleanup function throws
-and error it is ignored by default. The register
-function supports an optional second `options` argument that lets you configure a rethrow
-strategy so that error in the cleanup function is rethrown.
+By default, if a cleanup function throws an error after the main function has thrown an error, the cleanup error will be ignored. You can customize this behavior by passing `{ rethrow: true }` to the `register` function to have it rethrow cleanup errors instead.
+
+### Use cases
+
+#### Clean up temporary files
 
 ```ts
 import * as _ from 'radashi'
 
+// Placeholder functions
 const createBuildDir = async () => {
-  /* create build dir... */
+  console.log('Creating build directory...')
+  await _.sleep(100)
+  console.log('Build directory created.')
+  return 'build'
 }
 const build = async () => {
-  /* build project... */
+  console.log('Building project...')
+  await _.sleep(100)
+  console.log('Project built.')
 }
 
 await _.defer(async cleanup => {
@@ -35,23 +38,36 @@ await _.defer(async cleanup => {
 
   await build()
 })
+```
 
+#### Clean up resources in an API
+
+```ts
+// Placeholder API
 const api = {
   org: {
     create: async () => ({ id: 1 }),
     delete: async () => {
-      /* delete org... */
+      console.log('Deleting organization...')
+      await _.sleep(100)
+      console.log('Deleted organization.')
     },
   },
   user: {
     create: async () => ({ id: 2 }),
     delete: async () => {
-      /* delete delete... */
+      console.log('Deleting user...')
+      await _.sleep(100)
+      console.log('Deleted user.')
     },
   },
 }
+
+// Placeholder test function
 const executeTest = async () => {
-  /* exec text... */
+  console.log('Executing test...')
+  await _.sleep(100)
+  console.log('Test complete.')
 }
 
 await _.defer(async register => {