platform_string() feeds the CDP Emulation.setUserAgentOverride 'platform' field,
which sets the LEGACY navigator.platform. It was returning the UA-CH form
("macOS"/"Linux") — but real Chrome reports navigator.platform = "MacIntel" on
macOS and "Linux x86_64" on Linux. "macOS" contradicts the UA's "Intel Mac OS X"
and is a trivial bot-detection tell (platform vs UA mismatch). UA-CH
(navigator.userAgentData.platform via platform_hint) stays "macOS"/"Windows"/
"Linux" — that form is correct there.
Verified locally on bot.sannysoft.com (all rows green incl. navigator.platform=
MacIntel) + eval probes: webdriver false, no Headless in UA, real WebGL
(Apple M3 Metal, not SwiftShader), plugins/permissions consistent.