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-browser/src/page.rs

@@ -267,6 +267,11 @@ impl Page {
         if let Ok(ua) = self.http_client.user_agent.try_read() {
             rt.set_user_agent(&ua);
         }
+        rt.set_platform(
+            &self.context.platform,
+            &self.context.ua_platform,
+            &self.context.ua_platform_version,
+        );
 
         rt.set_cookie_jar(self.context.cookie_jar.clone());
         rt.set_http_client(self.http_client.clone());