Expand startProcess() options documentation

Add comprehensive documentation for all startProcess() options including
timeout, processId, encoding, and autoCleanup parameters that were missing
from the API reference.

🤖 Generated with Claude Code

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

Author: github-actions[bot]

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

@@ -131,8 +131,12 @@ const process = await sandbox.startProcess(command: string, options?: ProcessOpt
 **Parameters**:
 - `command` - The command to start as a background process
 - `options` (optional):
-  - `cwd` - Working directory
-  - `env` - Environment variables
+  - `cwd` - Working directory for this process
+  - `env` - Environment variables for this process
+  - `timeout` - Maximum execution time in milliseconds
+  - `processId` - Custom process ID (auto-generated if not provided)
+  - `encoding` - Output encoding (default: `"utf-8"`)
+  - `autoCleanup` - Automatically cleanup process resources (default: `true`)
 
 **Returns**: `Promise<ProcessInfo>` with `id`, `pid`, `command`, `status`