fix(playwright): add retainLines to preserve source line numbers

[omarshibli]

Problem

Babel's compact: false expands destructured parameters across multiple lines in the compiled output, causing cumulative line drift:

Source line 7:  test('first', async ({ foo, bar, baz }) => {
Source line 10: test('second', async ({ foo, bar, baz }) => {
Source line 13: test('third', async ({ foo, bar, baz }) => {

Compiled (without retainLines) — 15 source lines become 30 compiled lines:
Line 9:  test('first', async ({    → +2 drift
Line 16: test('second', async ({   → +6 drift
Line 23: test('third', async ({    → +10 drift

Each destructured pattern with N parameters expands from 1 line to N+2 lines. The drift grows with each pattern, compounding across the file.

Why source maps alone don't cover this

While sourceMapSupport correctly resolves line numbers in the test report path (wrapFunctionWithLocation → sourceMapSupport.wrapCallSite), the Playwright Inspector (PWDEBUG=1) uses a different code path:

1. captureRawStack() captures Error.stack → parseStackFrame() extracts line numbers
2. Line numbers are sent as metadata.location to the server
3. Recorder._updateUserSources() uses metadata.location.line directly to highlight lines in the source file

Additionally, retainLines: true makes the source map trivially correct (1:1 line mapping), eliminating any potential for source map inaccuracies with complex transformations.

Fix

One-line change: add retainLines: true to babel transform options. This tells babel to keep statements on their original lines, preserving line number alignment between source and compiled output.

Test

The test calls babelTransform() directly and verifies that test() calls with destructured TypeScript parameters remain on their original source lines (7, 10, 13) in the compiled output. This test fails without retainLines: true (lines shift to 9, 16, 23).

Related Issues

• [Bug]: Wrong line numbers in reports with type: module in package.json and Node.js 24.12.0 #38578 — Wrong line numbers in reports
• [Bug]: test decorations shown in the editor gutter may display in the wrong position #38804 — Test decorations shown in wrong position

[omarshibli]

I've made previous attempt to fix it here #39217 but got it rejected, i've revisited the tests and fix the issues raised in the previous PR.

[Skn0tt]

As per #39217 (comment), please start with filing a bug report. Thank you.