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, 118 insertions, 0 deletions

diff --git a/legacy-cpp/src/platform/macos_platform.h b/legacy-cpp/src/platform/macos_platform.h
new file mode 100644
index 0000000..39dc3db
--- /dev/null
+++ b/legacy-cpp/src/platform/macos_platform.h
@@ -0,0 +1,118 @@
+#ifndef SRDWM_MACOS_PLATFORM_H
+#define SRDWM_MACOS_PLATFORM_H
+
+#include "platform.h"
+#include <memory>
+#include <string>
+#include <map>
+
+// Forward declarations for macOS
+#ifdef __APPLE__
+typedef struct CGSRDWindow* CGSRDWindowRef;
+typedef struct CGEvent* CGEventRef;
+typedef struct CGDisplay* CGDirectDisplayID;
+typedef struct CGMenu* CGMenuRef;
+typedef struct CGMenuBar* CGMenuBarRef;
+#endif
+
+class MacOSPlatform : public Platform {
+public:
+    MacOSPlatform();
+    ~MacOSPlatform() override;
+
+    // Platform interface implementation
+    bool initialize() override;
+    void shutdown() override;
+    
+    bool poll_events(std::vector<Event>& events) override;
+    void process_event(const Event& event) override;
+    
+    std::unique_ptr<SRDWindow> create_window(const std::string& title, int x, int y, int width, int height) override;
+    void destroy_window(SRDWindow* window) override;
+    void set_window_position(SRDWindow* window, int x, int y) override;
+    void set_window_size(SRDWindow* window, int width, int height) override;
+    void set_window_title(SRDWindow* window, const std::string& title) override;
+    void focus_window(SRDWindow* window) override;
+    void minimize_window(SRDWindow* window) override;
+    void maximize_window(SRDWindow* window) override;
+    void close_window(SRDWindow* window) override;
+    
+    std::vector<Monitor> get_monitors() override;
+    Monitor get_primary_monitor() override;
+    
+    void grab_keyboard() override;
+    void ungrab_keyboard() override;
+    void grab_pointer() override;
+    void ungrab_pointer() override;
+    
+    // SRDWindow decorations (macOS implementation)
+    void set_window_decorations(SRDWindow* window, bool enabled) override;
+    void set_window_border_color(SRDWindow* window, int r, int g, int b) override;
+    void set_window_border_width(SRDWindow* window, int width) override;
+    bool get_window_decorations(SRDWindow* window) const override;
+
+    // macOS-specific features
+    void setup_global_menu();
+    void update_global_menu(const std::string& app_name);
+    void set_menu_bar_visible(bool visible);
+    void set_dock_visible(bool visible);
+    void set_spaces_enabled(bool enabled);
+    void switch_to_space(int space_id);
+    int get_current_space() const;
+    std::vector<int> get_available_spaces() const;
+    
+    // Mission Control and Spaces
+    void show_mission_control();
+    void show_app_expose();
+    void show_desktop();
+    
+    // Window management enhancements
+    void set_window_level(SRDWindow* window, int level);
+    void set_window_shadow(SRDWindow* window, bool enabled);
+    void set_window_blur(SRDWindow* window, bool enabled);
+    void set_window_alpha(SRDWindow* window, float alpha);
+
+    std::string get_platform_name() const override;
+    bool is_wayland() const override;
+    bool is_x11() const override;
+    bool is_windows() const override;
+    bool is_macos() const override;
+
+private:
+    bool initialized_;
+    std::map<CGSRDWindowRef, SRDWindow*> window_map_;
+    std::vector<Monitor> monitors_;
+    
+    // Decoration state (macOS limitations)
+    bool decorations_enabled_;
+    std::map<CGSRDWindowRef, CGSRDWindowRef> overlay_window_map_; // window -> overlay
+    
+    // macOS-specific state
+    bool global_menu_enabled_;
+    bool dock_visible_;
+    bool spaces_enabled_;
+    CGMenuBarRef menu_bar_;
+    std::map<std::string, CGMenuRef> app_menus_;
+    
+    // Event handling
+    void setup_event_tap();
+    void remove_event_tap();
+    
+    // Monitor management
+    void update_monitors();
+    
+    // Utility methods
+    SRDWindow* find_window_by_cgwindow(CGSRDWindowRef cgwindow);
+    
+    // Decoration methods (macOS limitations)
+    void create_overlay_window(SRDWindow* window);
+    void destroy_overlay_window(SRDWindow* window);
+    
+    // Global menu methods
+    void create_app_menu(const std::string& app_name);
+    void update_menu_bar();
+    void handle_menu_event(CGEventRef event);
+};
+
+#endif // SRDWM_MACOS_PLATFORM_H
+