test runner, cross-target runners, lib/exe split

- subprocess-isolated test runner (replaces V1 dlopen-RunTest);
  Pass/Fail/Crash/Timeout/Skipped outcomes via :Test partition
- TestRunner abstraction with command templates: Local, Ssh,
  SshWin (cmd.exe-shell), QemuUser, FromEnv; probe-based skip
  when runner unreachable
- transitive PCM-path propagation in Build(); resolveImport
  walks deps recursively; depResults cache keyed by PcmDir()
  so per-target builds don't collide
- cfg.sysroot threaded through BuildStdPcm + base compile/link
  command (enables aarch64 cross via Arch Linux ARM rootfs)
- lib + exe split: project.cpp defines crafterBuildLib
  (LibraryStatic) + crafterBuildExe (Executable depending on
  it); build.sh produces lib/libcrafter-build.a alongside
  bin/crafter-build for downstream static-link consumers
- Windows DLL+launcher: CRAFTER_API macro, /EXPORT flag for
  project.dll's CrafterBuildProject; Crafter::Run as the real
  entry point with main.cpp as a thin wrapper
- 18 tests: HelloWorld/WithModule/Defines/CrossProjectModule/
  Diamond × (Linux + sshwin:winvm), plus Incremental,
  BuildError, Libraries, RunnerClassification, QemuUser,
  SshRunner, WindowsViaSsh, CrossArchAarch64
- single ./bin/crafter-build test runs everything; Windows
  variants skip gracefully if winvm SSH alias unreachable

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

tests/fixtures/libraries/project.cpp

@@ -0,0 +1,47 @@
+import std;
+import Crafter.Build;
+namespace fs = std::filesystem;
+using namespace Crafter;
+
+extern "C" Configuration CrafterBuildProject(std::span<const std::string_view>) {
+    static auto MathStatic = std::make_unique<Configuration>();
+    MathStatic->path = "./mathlib/";
+    MathStatic->name = "MathLib";
+    MathStatic->outputName = "MathLib";
+    MathStatic->target = "x86_64-pc-linux-gnu";
+    MathStatic->type = ConfigurationType::LibraryStatic;
+    {
+        std::array<fs::path, 1> ifaces = { "MathLib" };
+        std::array<fs::path, 0> impls = {};
+        MathStatic->GetInterfacesAndImplementations(ifaces, impls);
+    }
+
+    static auto GreetDynamic = std::make_unique<Configuration>();
+    GreetDynamic->path = "./greetlib/";
+    GreetDynamic->name = "GreetLib";
+    GreetDynamic->outputName = "GreetLib";
+    GreetDynamic->target = "x86_64-pc-linux-gnu";
+    GreetDynamic->type = ConfigurationType::LibraryDynamic;
+    {
+        std::array<fs::path, 1> ifaces = { "GreetLib" };
+        std::array<fs::path, 0> impls = {};
+        GreetDynamic->GetInterfacesAndImplementations(ifaces, impls);
+    }
+
+    Configuration app;
+    app.path = "./";
+    app.name = "libs-app";
+    app.outputName = "libs-app";
+    app.target = "x86_64-pc-linux-gnu";
+    app.type = ConfigurationType::Executable;
+    app.dependencies = { MathStatic.get(), GreetDynamic.get() };
+    {
+        std::array<fs::path, 0> ifaces = {};
+        std::array<fs::path, 1> impls = { "main" };
+        app.GetInterfacesAndImplementations(ifaces, impls);
+    }
+    app.linkFlags.push_back("-Wl,--export-dynamic");
+    app.linkFlags.push_back("-ldl");
+
+    return app;
+}