fix: handle proxy authentication via CDP Fetch.authRequired (#1000)

* fix: handle proxy authentication via CDP Fetch.authRequired

Chrome's --proxy-server flag does not support credentials embedded in
the URL. When a proxy requires authentication, Chrome receives a 407
from the proxy but has no way to respond with credentials, resulting
in net::ERR_INVALID_AUTH_CREDENTIALS.

Fix by:
1. Parsing credentials from the proxy URL (already done by parse_proxy)
2. Storing them in DaemonState.proxy_credentials
3. Enabling Fetch.enable with handleAuthRequests: true
4. Responding to Fetch.authRequired events with Fetch.continueWithAuth
5. Passing only the server URL (without credentials) to --proxy-server
6. Forwarding credentials to the daemon via dedicated env vars

Also adds fallback to standard proxy env vars (HTTP_PROXY, HTTPS_PROXY,
ALL_PROXY, NO_PROXY) when AGENT_BROWSER_PROXY is not set.

Fixes #990

* refactor: use typed struct for parse_proxy, fix double Fetch.enable and username-only auth

- Replace serde_json::Value return from parse_proxy with a typed ParsedProxy struct
- Fix double Fetch.enable call when both proxy auth and domain filter are active
  (the second call could overwrite handleAuthRequests from the first)
- Allow username-only proxy auth (some proxies don't require a password)
- Handle empty username/password in parse_proxy as None instead of Some("")
- Use install_domain_filter_fetch in auto_launch for consistency
- Update unit tests to use typed struct fields

---------

Co-authored-by: ctate <366502+ctate@users.noreply.github.com>

cli/src/native/network.rs

@@ -233,15 +233,16 @@ pub async fn install_domain_filter_script(
 pub async fn install_domain_filter_fetch(
     client: &CdpClient,
     session_id: &str,
+    handle_auth_requests: bool,
 ) -> Result<(), String> {
+    let mut params = json!({
+        "patterns": [{ "urlPattern": "*" }]
+    });
+    if handle_auth_requests {
+        params["handleAuthRequests"] = json!(true);
+    }
     client
-        .send_command(
-            "Fetch.enable",
-            Some(json!({
-                "patterns": [{ "urlPattern": "*" }]
-            })),
-            Some(session_id),
-        )
+        .send_command("Fetch.enable", Some(params), Some(session_id))
         .await?;
     Ok(())
 }
@@ -253,9 +254,10 @@ pub async fn install_domain_filter(
     client: &CdpClient,
     session_id: &str,
     allowed_domains: &[String],
+    handle_auth_requests: bool,
 ) -> Result<(), String> {
     install_domain_filter_script(client, session_id, allowed_domains).await?;
-    install_domain_filter_fetch(client, session_id).await?;
+    install_domain_filter_fetch(client, session_id, handle_auth_requests).await?;
     Ok(())
 }