Rewrite srdwm in Rust: working X11 and Wayland backends, Lua config

The C++ prototype (moved to legacy-cpp/) was mostly a design skeleton:
X11 and Windows backends were partially real, Wayland created the
wlroots object graph but never wired a single event listener, macOS
was stub except monitor enumeration, and the Lua engine's srd.bind()
stored a key-combo string but never the actual closure. See
docs/PRIOR_ART.md for the full audit.

This replaces it with a Cargo workspace:

- srdwm-core: platform-independent window/workspace/monitor state,
  a real master-stack tiling layout, and SmartPlacement grid/cascade/
  snap-to-edge placement - fixing several bugs in the C++ version
  (hardcoded 2-column grid, cascade that never cascaded, snap-to-edge
  that always returned a fixed rect). 35 unit tests.
- srdwm-config: the srd Lua API via mlua, implementing the surface
  docs/DEFAULTS.md always documented but the C++ engine never actually
  built (srd.window.close()/focus(direction), srd.workspace.next(),
  real keybinding closures, require("srd") support). 10 unit tests.
- srdwm-x11: a real reparenting WM with a drawn title bar (buttons,
  drag, resize), verified live under Xephyr - frame placement and
  client offset match srdwm-core's computed geometry exactly, and the
  decoration renders correctly on screen.
- srdwm-wayland: a from-scratch smithay compositor (the C++ version
  had nothing working to port from) - runs via the winit backend,
  tracks xdg-shell toplevels through the same WindowManager and
  hit-testing code X11 uses, verified to start/render/run without
  crashing. Decorations are solid-color (no text yet); see
  docs/IMPLEMENTATION_STATUS.md for exact scope.
- srdwm-windows / srdwm-macos: structured, cfg-gated designs informed
  by komorebi/glazewm and yabai/AeroSpace respectively (see
  docs/PRIOR_ART.md), honestly marked as unbuilt/unverified since this
  sandbox has no Windows or macOS target.

1 files changed, 100 insertions, 0 deletions

diff --git a/legacy-cpp/tests/test_windows_platform.cc b/legacy-cpp/tests/test_windows_platform.cc
new file mode 100644
index 0000000..f4d313b
--- /dev/null
+++ b/legacy-cpp/tests/test_windows_platform.cc
@@ -0,0 +1,100 @@
+#include <gtest/gtest.h>
+#include "../src/platform/windows_platform.h"
+#include <memory>
+
+class WindowsPlatformTest : public ::testing::Test {
+protected:
+    void SetUp() override {
+        platform = std::make_unique<WindowsPlatform>();
+    }
+    
+    void TearDown() override {
+        if (platform) {
+            platform->shutdown();
+        }
+    }
+    
+    std::unique_ptr<WindowsPlatform> platform;
+};
+
+TEST_F(WindowsPlatformTest, Initialization) {
+    bool initialized = platform->initialize();
+    
+    if (initialized) {
+        EXPECT_TRUE(platform->get_platform_name() == "Windows");
+        EXPECT_TRUE(platform->is_windows());
+        EXPECT_FALSE(platform->is_x11());
+        EXPECT_FALSE(platform->is_wayland());
+        EXPECT_FALSE(platform->is_macos());
+    }
+}
+
+TEST_F(WindowsPlatformTest, PlatformCapabilities) {
+    EXPECT_TRUE(platform->get_platform_name() == "Windows");
+    EXPECT_TRUE(platform->is_windows());
+    EXPECT_FALSE(platform->is_x11());
+    EXPECT_FALSE(platform->is_wayland());
+    EXPECT_FALSE(platform->is_macos());
+}
+
+TEST_F(WindowsPlatformTest, MonitorDetection) {
+    if (platform->initialize()) {
+        auto monitors = platform->get_monitors();
+        EXPECT_FALSE(monitors.empty());
+        
+        for (const auto& monitor : monitors) {
+            EXPECT_GT(monitor.id, 0);
+            EXPECT_FALSE(monitor.name.empty());
+            EXPECT_GT(monitor.width, 0);
+            EXPECT_GT(monitor.height, 0);
+            EXPECT_GT(monitor.refresh_rate, 0);
+        }
+    }
+}
+
+TEST_F(WindowsPlatformTest, WindowCreation) {
+    if (platform->initialize()) {
+        auto window = platform->create_window("Windows Test Window", 100, 100, 400, 300);
+        EXPECT_NE(window, nullptr);
+        
+        if (window) {
+            EXPECT_EQ(window->getTitle(), "Windows Test Window");
+            EXPECT_EQ(window->getX(), 100);
+            EXPECT_EQ(window->getY(), 100);
+            EXPECT_EQ(window->getWidth(), 400);
+            EXPECT_EQ(window->getHeight(), 300);
+        }
+    }
+}
+
+TEST_F(WindowsPlatformTest, DWMIntegration) {
+    if (platform->initialize()) {
+        auto window = platform->create_window("Windows Test Window", 100, 100, 400, 300);
+        EXPECT_NE(window, nullptr);
+        
+        if (window) {
+            // Test DWM border color API
+            platform->set_window_border_color(window.get(), 255, 0, 0);
+            
+            // Test border width
+            platform->set_window_border_width(window.get(), 5);
+            
+            platform->destroy_window(window.get());
+        }
+    }
+}
+
+TEST_F(WindowsPlatformTest, EventPolling) {
+    if (platform->initialize()) {
+        std::vector<Event> events;
+        bool result = platform->poll_events(events);
+        
+        // Should not crash, even if no events are available
+        EXPECT_TRUE(result || events.empty());
+    }
+}
+
+int main(int argc, char **argv) {
+    ::testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}