fix: maintain custom sandbox identifier after file changes

When running sandbox with --identifier flag, the custom identifier
now persists throughout the entire session, including after file
changes trigger rebuilds.

Previously, the identifier would fall back to default (whoami) after
file changes because printSandboxNameInfo() was called without passing
the sandboxIdentifier parameter.

Fixes #2874

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

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

Author: alexlau811

packages/sandbox/src/file_watching_sandbox.ts

@@ -221,7 +221,7 @@ export class FileWatchingSandbox extends EventEmitter implements Sandbox {
               this.filesChangesTracker.trackFileChange(filePath);
               if (latch === 'open') {
                 this.printer.clearConsole();
-                await this.printSandboxNameInfo();
+                await this.printSandboxNameInfo(options.identifier);
               }
               this.printer.log(
                 `[Sandbox] Triggered due to a file ${eventName} event: ${path.relative(