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-js/src/runtime.rs

@@ -153,6 +153,13 @@ impl ObscuraJsRuntime {
         self.state.borrow_mut().http_client = Some(client);
     }
 
+    /// Install the stealth (wreq) HTTP client so scripted fetch()/XHR is routed
+    /// through it in stealth mode (see op_fetch_url / stealth_fetch_all).
+    #[cfg(feature = "stealth")]
+    pub fn set_stealth_client(&self, client: std::sync::Arc<obscura_net::StealthHttpClient>) {
+        self.state.borrow_mut().stealth_client = Some(client);
+    }
+
     pub fn set_dom(&self, dom: DomTree) {
         self.state.borrow_mut().dom = Some(dom);
     }