V2: WASI, -r flag, CI pipeline, examples & tests cleanup

WASI / wasm32 target support
- Auto-detect /usr/share/wasi-sysroot on Linux when target starts_with("wasm32")
- Skip -march/-mtune for wasm (clang rejects them)
- Apply -fno-exceptions -fno-c++-static-destructors -mllvm -wasm-enable-sjlj
  -D_WASI_EMULATED_SIGNAL to wasm builds (compile + std PCM, kept in sync)
- .wasm output extension in expectedOutputFor and link command
- EnableWasiBrowserRuntime(cfg): opt-in helper that drops index.html +
  runtime.js next to the .wasm; runtime.js reads window.CRAFTER_WASM_URL
  set in the templated index.html so a single shim handles any output name

-r run flag in the CLI: build then exec the artifact (host targets only;
  rejects libraries; auto .exe/.wasm extension handling)

CI pipeline (.forgejo/workflows/ci.yaml)
- Triggers: PR/push to master + manual dispatch
- Single arch-latest container job: install deps, bootstrap, self-rebuild,
  run tests, cross-compile mingw, package both archives, upload artifacts
- Rolling 'latest' release published only on push/dispatch to master

mingw cross-compile from Linux now works end-to-end:
- ExternalDependency cache key includes target so per-target glslang builds
  don't collide; CMAKE_BUILD_TYPE=Release pinned (otherwise glslang appends
  'd' to lib names and breaks linking); cross-compile cmake flags
  (CMAKE_SYSTEM_NAME=Windows, CMAKE_*_COMPILER_TARGET=...)
- project.cpp accepts --target=<triple>; Linux-only -Wl,--export-dynamic
  and -ldl are gated; mingw glslang skips the standalone exe (its libgcc_eh
  link pulls pthread which mingw doesn't link by default)
- mingw compile uses -femulated-tls so std::__once_callable etc reference
  the same emutls symbols libstdc++ provides
- mingw link auto-adds -lstdc++exp -lpthread

GetCrafterBuildHome() exposed from the Platform module; LoadProject (Linux
+ Windows) now both use it instead of duplicating the resolution.

Examples reorg: hello-world, library, with-module, wasi, tests — each with
its own README. Tests reorg: per-test directory with inner/ fixture, no
shared tests/fixtures/ tree. New Wasi test verifies .wasm magic bytes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/_shared/TestUtil.h

@@ -0,0 +1,76 @@
+#pragma once
+#include <stdlib.h>  // setenv (POSIX, not in `import std`)
+
+namespace TestUtil {
+    // Exit code 77 follows the autoconf convention. crafter-build's test
+    // runner maps it to TestOutcome::Skipped and renders the test's stdout
+    // as the reason. Use this when the test discovers at runtime that its
+    // preconditions aren't met (tool missing, env unset, etc).
+    [[noreturn]] inline void Skip(std::string_view reason) {
+        std::print("{}", reason);
+        std::exit(77);
+    }
+
+    inline std::string ReadFile(const std::filesystem::path& p) {
+        std::ifstream f(p);
+        std::stringstream ss;
+        ss << f.rdbuf();
+        return ss.str();
+    }
+
+    inline std::filesystem::path CopyFixtureToTemp(std::string_view testName, const std::filesystem::path& source) {
+        namespace fs = std::filesystem;
+        fs::path tmp = fs::temp_directory_path() / std::format("crafter-test-{}", testName);
+        fs::remove_all(tmp);
+        fs::copy(source, tmp, fs::copy_options::recursive);
+        return tmp;
+    }
+
+    struct CmdResult {
+        int exitCode;
+        std::string output;
+    };
+
+    inline CmdResult RunInDir(const std::filesystem::path& cwd, std::string_view command) {
+        namespace fs = std::filesystem;
+        // Log inside cwd so parallel test drivers don't trample each other.
+        fs::path log = cwd / ".crafter-cmd-output.log";
+        std::string cmd = std::format("cd '{}' && {} > '{}' 2>&1",
+            cwd.string(), command, log.string());
+        int rc = std::system(cmd.c_str());
+        std::string out = ReadFile(log);
+        std::error_code ec;
+        fs::remove(log, ec);
+        return {rc, std::move(out)};
+    }
+
+    // Build cfg with a fresh dep cache. Convenient for outer-driver tests that
+    // exercise the build API in-process and don't need to share the dep cache
+    // across multiple Build() calls.
+    inline Crafter::BuildResult BuildOnce(Crafter::Configuration& cfg) {
+        std::unordered_map<std::filesystem::path, std::shared_future<Crafter::BuildResult>> depResults;
+        std::mutex depMutex;
+        return Crafter::Build(cfg, depResults, depMutex);
+    }
+
+    // Copy a fixture into a fresh temp dir, chdir there (so cfg.path = "./"
+    // inside the inner project.cpp resolves to the temp dir), and load its
+    // project.cpp. Common prep for in-process build/test API tests.
+    //
+    // Also sets CRAFTER_BUILD_HOME to <projectRoot>/share/crafter-build before
+    // loading. The lib's default sourceDir is derived from /proc/self/exe, but
+    // test exes live in tests/<Name>/bin/... rather than next to the project's
+    // share/, so the default lookup misses. The test runner launches tests
+    // with cwd = project root, so we capture that here before the chdir below.
+    inline Crafter::Configuration LoadFixture(std::string_view testName,
+                                              const std::filesystem::path& source,
+                                              std::span<const std::string_view> args = {}) {
+        auto projectRoot = std::filesystem::current_path();
+        auto sharePath = projectRoot / "share" / "crafter-build";
+        ::setenv("CRAFTER_BUILD_HOME", sharePath.string().c_str(), 1);
+
+        auto work = CopyFixtureToTemp(testName, source);
+        std::filesystem::current_path(work);
+        return Crafter::LoadProject("project.cpp", args);
+    }
+}