fix(cdp): emit Network events for script-initiated requests (#415)

Requests made by page JS (fetch/XHR/dynamic script and stylesheet loads)
run in the V8 op layer and never produced a NetworkEvent, so CDP emitted
Network.requestWillBeSent / responseReceived only for the static
navigation subresources. Puppeteer/Playwright page.on('request') and
on('response') therefore missed every XHR/JSON response, which breaks
response capture (and is the root cause of the Aviasales half of #394).

op_fetch_url now records a JsNetworkEvent keyed by the same fetch-{N} id
under which it already stores the response body. The Page drains these
into its network_events before the CDP layer emits, so they flow through
emit_navigation_events as requestWillBeSent / responseReceived /
loadingFinished alongside the document subresources, and
Network.getResponseBody resolves for them via the shared id. Applied to
both navigation paths (server process_navigation and in-process
do_navigate). The queue is capped at 4096 events per page.

Closes #406.

crates/obscura-browser/src/page.rs

@@ -1256,6 +1256,32 @@ impl Page {
         self.js.as_ref().map(|js| js.fetched_urls()).unwrap_or_default()
     }
 
+    /// Move network events recorded for script-initiated requests
+    /// (fetch/XHR/dynamic resource) from the JS runtime into this page's
+    /// network_events, so the CDP layer emits Network.requestWillBeSent /
+    /// responseReceived for them (issue #406). Idempotent: the runtime's queue
+    /// is drained, so calling this repeatedly does not duplicate events. The
+    /// fetch-{N} request id is preserved so Network.getResponseBody resolves.
+    pub fn sync_js_network_events(&mut self) {
+        let events = match self.js.as_ref() {
+            Some(js) => js.take_js_network_events(),
+            None => return,
+        };
+        for ev in events {
+            self.network_events.push(NetworkEvent {
+                request_id: ev.request_id,
+                url: ev.url,
+                method: ev.method,
+                resource_type: "Fetch".to_string(),
+                status: ev.status,
+                headers: std::collections::HashMap::new(),
+                response_headers: Arc::new(ev.response_headers),
+                body_size: ev.body_size,
+                timestamp: ev.timestamp,
+            });
+        }
+    }
+
     pub fn dom(&self) -> Option<&DomTree> {
         self.dom.as_ref()
     }