e2e-test: better env var for browser trace (#6093)

### Summary
I noticed that traces weren’t attaching for browser failures/retries in
CI only since my change yesterday. After some investigation, I realized
the issue was caused by an environment variable not containing the value
I expected. To resolve this, I selected a more reliable environment
variable that’s compatible with CI runs, ensuring it correctly
determines whether the tests are being run via the CLI.

### QA Notes
* [Triggered a browser/web
failure](https://d38p2avprg8il3.cloudfront.net/playwright-report-12930854312-27797/index.html#?testId=d3c3813350b4cc7e69da-d3305c7a59dec61b969f)
and confirmed trace is now attached.

test/e2e/tests/_test.setup.ts

@@ -263,8 +263,8 @@ export const test = base.extend<TestFixtures, WorkerFixtures>({
 	}, { auto: true }],
 
 	tracing: [async ({ app }, use, testInfo) => {
-		// Determine environment and mode
-		const isCommandLineRun = process.env.TERM_PROGRAM === 'vscode' && !(process.env.PW_UI_MODE === 'true');
+		// Determine execution mode
+		const isCommandLineRun = process.env.npm_execpath && !(process.env.PW_UI_MODE === 'true');
 
 		// Use default built-in tracing for e2e-browser except when running via CLI
 		if (testInfo.project.name === 'e2e-browser' && !isCommandLineRun) {