fix: harden private host detection against SSRF bypass via IP parsing

Security fix for browser tool SSRF prevention via proper IP parsing.

src/tools/browser.rs

@@ -790,6 +790,25 @@ mod tests {
         );
     }
 
+    #[test]
+    fn extract_host_handles_ipv6() {
+        // IPv6 with brackets (required for URLs with ports)
+        assert_eq!(
+            extract_host("https://[::1]/path").unwrap(),
+            "[::1]"
+        );
+        // IPv6 with brackets and port
+        assert_eq!(
+            extract_host("https://[2001:db8::1]:8080/path").unwrap(),
+            "[2001:db8::1]"
+        );
+        // IPv6 with brackets, trailing slash
+        assert_eq!(
+            extract_host("https://[fe80::1]/").unwrap(),
+            "[fe80::1]"
+        );
+    }
+
     #[test]
     fn is_private_host_detects_local() {
         assert!(is_private_host("localhost"));