test: broaden self-test coverage beyond the compile smoke test

The suite had only HelloWorld, which built and exited an empty exe. Add
in-process tests covering each public surface area users actually touch:

- StaticLib / ModuleInterface / DependencyLink — Build() against
  fixtures for libraries, project-local module interfaces, and
  cross-config module deps with link verification (runs the built exe).
- ShaderCompile — drives Shader::Compile directly, validates SPIR-V
  magic + Check() idempotency.
- StandardArgs — covers --debug, --target=, --march=, --mtune=,
  --lib/--shared promotions, and ArgQuery::Has / Get.
- TestRunnerSpec — FromSpec parse rules, ForTarget routing for host,
  wasm32-wasip1, aarch64-linux-gnu (+ sysroot QEMU_LD_PREFIX),
  i686 → qemu-i386 rewrite, mingw → wine on Linux hosts, FromEnv.
- VariantId — confirms type / debug / sysroot / defines / compileFlags /
  target / march all perturb the cache key, plus PcmDir routing.
- WasiBrowserRuntime — calls EnableWasiBrowserRuntime, asserts the
  three cfg.files entries get registered and index.html had its
  template placeholder substituted.
- RunSingleTestExit — drives RunSingleTest against tiny sh scripts and
  pins the documented exit-code mapping (0/77/non-zero) and the
  Cmd-prefix runner path.

Closes #12.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

project.cpp

@@ -98,6 +98,15 @@ extern "C" Configuration CrafterBuildProject(std::span<const std::string_view> a
     // Mirrors how downstream consumers link their own libraries into tests.
     if (cfg.target == "x86_64-pc-linux-gnu") {
         cfg.AddTest("HelloWorld").Dependencies({ crafterBuildLib.get() });
+        cfg.AddTest("StaticLib").Dependencies({ crafterBuildLib.get() });
+        cfg.AddTest("ModuleInterface").Dependencies({ crafterBuildLib.get() });
+        cfg.AddTest("DependencyLink").Dependencies({ crafterBuildLib.get() });
+        cfg.AddTest("ShaderCompile").Dependencies({ crafterBuildLib.get() });
+        cfg.AddTest("StandardArgs").Dependencies({ crafterBuildLib.get() });
+        cfg.AddTest("TestRunnerSpec").Dependencies({ crafterBuildLib.get() });
+        cfg.AddTest("VariantId").Dependencies({ crafterBuildLib.get() });
+        cfg.AddTest("WasiBrowserRuntime").Dependencies({ crafterBuildLib.get() });
+        cfg.AddTest("RunSingleTestExit").Dependencies({ crafterBuildLib.get() });
     }
 
     return cfg;