Merge stealth-overhaul into main

Resolved conflicts:
- page.rs: keep both set_blocked_urls (#315) and stealth client wiring
- ops.rs: keep SHA-512/224 + SHA-512/256 from stealth branch; keep
  the unreachable catch-all (vec![]) from #314 instead of silent
  SHA-256 fallback; updated comment accordingly
- bootstrap.js: extend the digest algorithm allowlist to include
  SHA-512/224 and SHA-512/256 to match the Rust additions

crates/obscura-browser/src/page.rs

@@ -286,9 +286,11 @@ impl Page {
         if self.stealth_client.is_some() {
             rt.set_stealth(true);
             rt.set_user_agent(obscura_net::STEALTH_USER_AGENT);
-            // Match platform to the Linux UA so navigator.platform and
-            // userAgentData.platform are consistent with navigator.userAgent.
-            rt.set_platform("Linux x86_64", "Linux", "");
+            rt.set_platform(
+                obscura_net::STEALTH_NAVIGATOR_PLATFORM,
+                obscura_net::STEALTH_UA_PLATFORM,
+                obscura_net::STEALTH_UA_PLATFORM_VERSION,
+            );
         } else {
             if let Ok(ua) = self.http_client.user_agent.try_read() {
                 rt.set_user_agent(&ua);
@@ -317,6 +319,10 @@ impl Page {
         rt.set_cookie_jar(self.context.cookie_jar.clone());
         rt.set_http_client(self.http_client.clone());
         rt.set_blocked_urls(self.blocked_url_patterns.clone());
+        #[cfg(feature = "stealth")]
+        if let Some(ref stealth) = self.stealth_client {
+            rt.set_stealth_client(stealth.clone());
+        }
 
         if let Some(tx) = &self.intercept_tx {
             rt.set_intercept_tx(tx.clone());