[M5+] add resolver::vcpkg_probe

tests/vcpkg_probe_live.cpp

@@ -0,0 +1,43 @@
+// Network-gated integration test for resolver::vcpkg_probe.
+
+#include <catch2/catch_test_macros.hpp>
+
+import cargoxx.resolver;
+import cargoxx.util;
+import std;
+
+namespace {
+
+auto network_tests_enabled() -> bool {
+    auto* env = std::getenv("CARGOXX_NETWORK_TESTS");
+    return env != nullptr && std::string_view{env} == "1";
+}
+
+} // namespace
+
+TEST_CASE("vcpkg_probe finds 'fmt' in microsoft/vcpkg",
+          "[resolver][network]") {
+    if (!network_tests_enabled()) {
+        SKIP("CARGOXX_NETWORK_TESTS != 1");
+    }
+    auto r = cargoxx::resolver::vcpkg_probe("fmt");
+    REQUIRE(r.has_value());
+    REQUIRE(r->find_package.starts_with("fmt"));
+    REQUIRE_FALSE(r->targets.empty());
+    // fmt's vcpkg port should expose at least one fmt:: target.
+    REQUIRE(std::ranges::any_of(r->targets, [](const std::string& t) {
+        return t.starts_with("fmt::");
+    }));
+}
+
+TEST_CASE("vcpkg_probe returns ResolutionUnknownPackage for a 404",
+          "[resolver][network]") {
+    if (!network_tests_enabled()) {
+        SKIP("CARGOXX_NETWORK_TESTS != 1");
+    }
+    auto r = cargoxx::resolver::vcpkg_probe(
+        "definitely_not_a_real_pkg_cargoxx_xyzzy");
+    REQUIRE_FALSE(r.has_value());
+    REQUIRE(r.error().code ==
+            cargoxx::util::ErrorCode::ResolutionUnknownPackage);
+}