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/connection.rs

@@ -188,6 +188,8 @@ pub struct DaemonOptions<'a> {
     pub user_agent: Option<&'a str>,
     pub proxy: Option<&'a str>,
     pub proxy_bypass: Option<&'a str>,
+    pub proxy_username: Option<&'a str>,
+    pub proxy_password: Option<&'a str>,
     pub ignore_https_errors: bool,
     pub allow_file_access: bool,
     pub profile: Option<&'a str>,
@@ -233,6 +235,12 @@ fn apply_daemon_env(cmd: &mut Command, session: &str, opts: &DaemonOptions) {
     if let Some(pb) = opts.proxy_bypass {
         cmd.env("AGENT_BROWSER_PROXY_BYPASS", pb);
     }
+    if let Some(pu) = opts.proxy_username {
+        cmd.env("AGENT_BROWSER_PROXY_USERNAME", pu);
+    }
+    if let Some(pp) = opts.proxy_password {
+        cmd.env("AGENT_BROWSER_PROXY_PASSWORD", pp);
+    }
     if opts.ignore_https_errors {
         cmd.env("AGENT_BROWSER_IGNORE_HTTPS_ERRORS", "1");
     }