fix(wasm): preserve binary fetch responses (#48)

* fix wasm response handling

* fix URL inputs in fetch polyfill

* test(wasm): cover binary fetch responses

crates/obscura-js/src/ops.rs

@@ -6,6 +6,7 @@ use std::sync::{Arc, OnceLock};
 use deno_core::op2;
 use deno_core::OpState;
 use deno_core::Extension;
+use base64::{engine::general_purpose::STANDARD as BASE64, Engine as _};
 use obscura_dom::{DomTree, NodeData, NodeId};
 use obscura_net::{CookieJar, ObscuraHttpClient};
 use tokio::sync::Mutex;
@@ -517,16 +518,19 @@ async fn op_fetch_url(
         }
     }
 
-    let resp_body = response
-        .text()
+    let resp_bytes = response
+        .bytes()
         .await
         .map_err(|e| deno_error::JsErrorBox::generic(e.to_string()))?;
+    let resp_body = String::from_utf8_lossy(&resp_bytes).to_string();
+    let resp_body_base64 = BASE64.encode(&resp_bytes);
 
     tracing::debug!("op_fetch_url completed: {} {} ({} bytes)", method, url, resp_body.len());
 
     Ok(serde_json::json!({
         "status": status,
         "body": resp_body,
+        "bodyBase64": resp_body_base64,
         "url": url,
         "headers": resp_headers,
     })