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/runner-classification/project.cpp

@@ -0,0 +1,33 @@
+import std;
+import Crafter.Build;
+namespace fs = std::filesystem;
+using namespace Crafter;
+
+extern "C" Configuration CrafterBuildProject(std::span<const std::string_view>) {
+    Configuration cfg;
+    cfg.path = "./";
+    cfg.name = "rc-meta";
+    cfg.outputName = "rc-meta";
+    cfg.target = "x86_64-pc-linux-gnu";
+    cfg.type = ConfigurationType::Executable;
+
+    auto addTest = [&](std::string name) {
+        Test t;
+        t.config.path = "./";
+        t.config.name = name;
+        t.config.outputName = name;
+        t.config.target = "x86_64-pc-linux-gnu";
+        t.config.type = ConfigurationType::Executable;
+        std::array<fs::path, 0> empty = {};
+        std::array<fs::path, 1> impls = { fs::path("tests") / name };
+        t.config.GetInterfacesAndImplementations(empty, impls);
+        cfg.tests.push_back(std::move(t));
+    };
+
+    addTest("Pass");
+    addTest("Fail");
+    addTest("Crash");
+    addTest("Hang");
+
+    return cfg;
+}