Document per-command env and cwd options for exec methods

Add documentation for new per-command environment variables and working
directory options in exec() and execStream() methods. These options
allow temporary configuration that does not persist in session state.

Includes examples showing:
- Setting per-command environment variables
- Specifying working directory per command
- Demonstrating that values do not persist across commands

Synced from cloudflare/sandbox-sdk PR #204

🤖 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

@@ -9,6 +9,10 @@ import { Details, TypeScriptExample } from "~/components";
 
 Execute commands and manage background processes in the sandbox's isolated container environment.
 
+:::note[Per-command vs Session-level options]
+Commands support per-command `env` and `cwd` options that apply only to that specific command execution. These do not persist in the session state. For persistent environment variables and working directories, use [session-level configuration](/sandbox/api/sessions/) with `createSession()`.
+:::
+
 ## Methods
 
 ### `exec()`
@@ -25,6 +29,8 @@ const result = await sandbox.exec(command: string, options?: ExecOptions): Promi
   - `stream` - Enable streaming callbacks (default: `false`)
   - `onOutput` - Callback for real-time output: `(stream: 'stdout' | 'stderr', data: string) => void`
   - `timeout` - Maximum execution time in milliseconds
+  - `env` - Environment variables for this command only (does not persist)
+  - `cwd` - Working directory for this command only (does not persist)
 
 **Returns**: `Promise<ExecuteResponse>` with `success`, `stdout`, `stderr`, `exitCode`
 
@@ -43,6 +49,22 @@ await sandbox.exec('npm install', {
   stream: true,
   onOutput: (stream, data) => console.log(`[${stream}] ${data}`)
 });
+
+// With per-command environment variables and directory
+await sandbox.exec('npm run build', {
+  env: { NODE_ENV: 'production', API_URL: 'https://api.example.com' },
+  cwd: '/workspace/my-project'
+});
+
+// Environment variables are scoped to this command only
+const result = await sandbox.exec('echo $TEMP_VAR', {
+  env: { TEMP_VAR: 'temporary-value' }
+});
+console.log(result.stdout); // "temporary-value"
+
+// TEMP_VAR is not available in subsequent commands
+const verify = await sandbox.exec('echo $TEMP_VAR');
+console.log(verify.stdout); // Empty - variable does not persist
 ```
 </TypeScriptExample>
 
@@ -56,7 +78,10 @@ const stream = await sandbox.execStream(command: string, options?: ExecOptions):
 
 **Parameters**:
 - `command` - The command to execute
-- `options` - Same as `exec()`
+- `options` (optional):
+  - `timeout` - Maximum execution time in milliseconds
+  - `env` - Environment variables for this command only (does not persist)
+  - `cwd` - Working directory for this command only (does not persist)
 
 **Returns**: `Promise<ReadableStream>` emitting `ExecEvent` objects (`start`, `stdout`, `stderr`, `complete`, `error`)
 
@@ -79,6 +104,19 @@ for await (const event of parseSSEStream<ExecEvent>(stream)) {
       break;
   }
 }
+
+// With per-command options
+const stream = await sandbox.execStream('python train.py', {
+  env: { MODEL_PATH: '/workspace/models', BATCH_SIZE: '32' },
+  cwd: '/workspace/ml-project',
+  timeout: 300000 // 5 minutes
+});
+
+for await (const event of parseSSEStream<ExecEvent>(stream)) {
+  if (event.type === 'stdout') {
+    console.log('Training:', event.data);
+  }
+}
 ```
 </TypeScriptExample>