fix: wire the HouseRules test only when this is the top-level project

crafter-build loads this project file as a `#pragma crafter dependency`
of its own project.cpp. The HouseRules test pulls crafter-build in via
GitProject so it can run the linter in-process, which from inside
crafter-build means loading crafter-build's project.cpp a second time,
which loads this file a second time, and the cycle guard throws. Every
crafter-build invocation that loads its project.cpp has failed since
the test was wired.

Guard the test with IsTopLevelProject(), which crafter-build exposes
for exactly this: it is false while a project file runs as somebody
else's dependency. Consumers never needed the test; only `crafter-build
test` run in this repository does.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

project.cpp

@@ -29,8 +29,11 @@ extern "C" Configuration CrafterBuildProject(std::span<const std::string_view> a
     // The rule test compiles the module as its own interface and links
     // crafter-build to run the linter in-process: from git by default, or
     // the sibling checkout with `crafter-build test --local`. Host only,
-    // like the rules themselves.
-    if (cfg.target == "x86_64-pc-linux-gnu") {
+    // like the rules themselves, and only when this is the project being
+    // built: crafter-build itself loads this file as a dependency, and the
+    // test's GitProject would then load crafter-build's project file again
+    // and recurse into the cycle guard.
+    if (IsTopLevelProject() && cfg.target == "x86_64-pc-linux-gnu") {
         Configuration* build = useLocal
             ? LocalProject({ .projectFile = "../Crafter.Build/project.cpp", .args = depArgs })
             : GitProject({ .source = { .url = "https://forgejo.catcrafts.net/Catcrafts/Crafter.Build.git" }, .args = depArgs });