Create the e2e trace directory before writing a trace (#2194)

`newPageOn` writes a trace into `traces/` when a test fails, and never created
that directory. It is gitignored, so a fresh checkout does not have it.

Traces were not in fact being dropped: the driver creates the parent of the
trace path itself, checked against the version this module pins rather than
assumed. The directory is created here anyway because nothing in the suite
states or tests that dependency, and the missing directory has been raised in
review on #2180 and again on #2193, each time needing the driver checked before
it could be answered.

One visible difference on a fresh checkout: the directory now arrives at 0750
rather than the 0755 the driver's own mkdir leaves, both measured. It runs only
on a test that has already failed, and logs its error rather than swallowing
it, matching the Stop call below it.

e2e/e2e_test.go

@@ -274,6 +274,11 @@ func newPageOn(t *testing.T, b playwright.Browser) playwright.Page {
 			// overwriting each other: the counter restarts with every process
 			name := strings.ReplaceAll(t.Name(), "/", "-")
 			path := filepath.Join(traceDir, fmt.Sprintf("%s-%d-%d.zip", name, os.Getpid(), seq))
+			// the driver creates the parent of the trace path too, but nothing here states or
+			// tests that, so the suite makes the directory itself
+			if derr := os.MkdirAll(traceDir, 0o750); derr != nil {
+				t.Logf("could not create %s: %v", traceDir, derr)
+			}
 			if serr := ctx.Tracing().Stop(path); serr != nil {
 				t.Logf("could not write the trace to %s: %v", path, serr)
 			}