Document process callback options and fix

Add comprehensive documentation for startProcess() callback options
(onStart, onOutput, onExit, onError) that were fixed in PR 267.

Changes:
- Add all ProcessOptions parameters to Commands API reference
- Add callback monitoring section to background processes guide
- Include practical examples showing real-time process monitoring

Fixes process callback documentation gap discovered in issue 262
where callbacks were broken and undocumented.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: github-actions[bot]

src/content/docs/sandbox/api/commands.mdx

@@ -95,10 +95,11 @@ const process = await sandbox.startProcess(command: string, options?: ProcessOpt
 - `options` (optional):
   - `cwd` - Working directory
   - `env` - Environment variables
-  - `onStart` - Callback when process starts: `(process: ProcessInfo) => void`
+  - `timeout` - Maximum execution time in milliseconds
+  - `onStart` - Callback when process starts: `(process: Process) => void`
   - `onOutput` - Callback for real-time output: `(stream: 'stdout' | 'stderr', data: string) => void`
-  - `onExit` - Callback when process completes: `(exitCode: number | null) => void`
-  - `onError` - Callback for errors: `(error: Error) => void`
+  - `onExit` - Callback when process exits: `(exitCode: number | null) => void`
+  - `onError` - Callback for process errors: `(error: Error) => void`
 
 **Returns**: `Promise<ProcessInfo>` with `id`, `pid`, `command`, `status`
 
@@ -113,19 +114,19 @@ const app = await sandbox.startProcess('node app.js', {
   env: { NODE_ENV: 'production', PORT: '3000' }
 });
 
-// With callbacks for real-time monitoring
+// With callbacks for monitoring
 const build = await sandbox.startProcess('npm run build', {
-  onStart: (proc) => {
-    console.log(`Build started with PID ${proc.pid}`);
+  onStart: (process) => {
+    console.log(`Process started with PID: ${process.pid}`);
   },
   onOutput: (stream, data) => {
     console.log(`[${stream}] ${data}`);
   },
   onExit: (exitCode) => {
-    console.log(`Build finished with exit code ${exitCode}`);
+    console.log(`Process exited with code: ${exitCode}`);
   },
   onError: (error) => {
-    console.error(`Build error: ${error.message}`)
+    console.error('Process error:', error.message);
   }
 });
 ```

src/content/docs/sandbox/guides/background-processes.mdx

@@ -70,36 +70,33 @@ Use callbacks for real-time process monitoring without manually streaming logs:
 
 <TypeScriptExample>
 ```
-const process = await sandbox.startProcess('npm run build', {
-  onStart: (proc) => {
-    console.log(`Build started with PID ${proc.pid}`);
+const server = await sandbox.startProcess('node server.js', {
+  onStart: (process) => {
+    console.log(`Server started with PID: ${process.pid}`);
   },
   onOutput: (stream, data) => {
-    // Handle output in real-time as it's produced
-    if (stream === 'stdout') {
-      console.log(data);
-    } else {
-      console.error(data);
-    }
+    // Real-time output from stdout/stderr
+    console.log(`[${stream}] ${data}`);
   },
   onExit: (exitCode) => {
     if (exitCode === 0) {
-      console.log('Build completed successfully');
+      console.log('Server stopped gracefully');
     } else {
-      console.error(`Build failed with exit code ${exitCode}`);
+      console.error(`Server crashed with code: ${exitCode}`);
     }
   },
   onError: (error) => {
-    console.error(`Build error: ${error.message}`);
+    console.error('Server error:', error.message);
   }
 });
 
-// Process monitoring happens in background
-// Your code continues immediately
+// Your code continues - callbacks fire in background
 ```
 </TypeScriptExample>
 
-Callbacks are useful when you need to react to process events without blocking your Worker execution or manually managing log streams.
+:::note[Callbacks vs streaming]
+Callbacks are ideal for background monitoring where you want to react to events without blocking. For detailed log analysis or waiting for specific output, use [`streamProcessLogs()`](/sandbox/api/commands/#streamprocesslogs) instead.
+:::
 
 ## Monitor process status