Stealth profile consistency (#269)

* feat(stealth): randomize browser profile per session

Add a pool of 8 realistic browser profiles (Win10/Win11/macOS, Chrome
143-146). One is picked randomly per BrowserContext instead of always
advertising Linux, which is a strong bot signal.

Each profile keeps navigator.platform, userAgentData.platform, and
userAgentData.platformVersion internally consistent with the UA string.

- profiles.rs: static PROFILES pool + random_profile() picker
- context.rs: pick profile on construction, store platform fields
- page.rs: call rt.set_platform() alongside rt.set_user_agent()
- runtime.rs: add set_platform() to inject __obscura_platform globals
- bootstrap.js: read platform/userAgentData from globals (default Win32)

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

* feat(stealth): match GPU renderer pool to OS profile

Windows profiles get ANGLE Direct3D11 renderers; macOS profiles get
ANGLE Metal renderers. Vendor strings updated to match (Google Inc. (Apple)
for Apple Silicon/Intel Mac, Google Inc. (NVIDIA/AMD/Intel) for Windows).

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

* fix(stealth): navigator.webdriver returns false instead of undefined

Browsers set navigator.webdriver to false when automation is not active.
Returning undefined is a detectable bot signal — fingerprinting scripts
check typeof navigator.webdriver === 'boolean' as part of headless detection.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

* Make stealth profile stable by default, rotation opt-in

Picking a random profile per BrowserContext meant one address would cycle
through different browser identities, which is itself a bot signal, and the
rotated profile carries no matching TLS or timezone fingerprint. Default to a
single stable profile; opt into rotation with OBSCURA_ROTATE_PROFILE, or pin
one with OBSCURA_PROFILE=<index>.

Drive timezone from the process TZ so Intl.DateTimeFormat and Date report one
consistent zone. Default Europe/Berlin; override with OBSCURA_TIMEZONE.

Update navigator.webdriver test to expect false, matching real Chrome.

---------

Co-authored-by: SGavrl <[email protected]>

crates/obscura-js/src/runtime.rs

@@ -206,6 +206,19 @@ impl ObscuraJsRuntime {
             format!("globalThis.__obscura_ua = '{}';", escaped),
         );
     }
+
+    pub fn set_platform(&mut self, platform: &str, ua_platform: &str, ua_platform_version: &str) {
+        let p = platform.replace('\'', "\\'");
+        let uap = ua_platform.replace('\'', "\\'");
+        let uapv = ua_platform_version.replace('\'', "\\'");
+        let _ = self.runtime.execute_script(
+            "<set-platform>",
+            format!(
+                "globalThis.__obscura_platform='{}';globalThis.__obscura_ua_platform='{}';globalThis.__obscura_ua_platform_version='{}';",
+                p, uap, uapv
+            ),
+        );
+    }
     pub fn evaluate(&mut self, expression: &str) -> Result<serde_json::Value, String> {
         let wrapped = Self::wrap_expression(expression);
         let result = self
@@ -1511,7 +1524,7 @@ mod tests {
         let ua = rt.evaluate("navigator.userAgent").unwrap();
         assert!(ua.as_str().unwrap().contains("Chrome"), "UA should contain Chrome: {}", ua);
         let wd = rt.evaluate("navigator.webdriver").unwrap();
-        assert_eq!(wd, serde_json::Value::Null);
+        assert_eq!(wd, serde_json::json!(false));
         let plugins = rt.evaluate("navigator.plugins.length").unwrap();
         assert!(plugins.as_f64().unwrap() > 0.0, "Should have plugins");
         let chrome = rt.evaluate("typeof window.chrome").unwrap();