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, 134 insertions, 0 deletions

diff --git a/legacy-cpp/src/core/event_system.h b/legacy-cpp/src/core/event_system.h
new file mode 100644
index 0000000..2af717b
--- /dev/null
+++ b/legacy-cpp/src/core/event_system.h
@@ -0,0 +1,134 @@
+#ifndef SRDWM_EVENT_SYSTEM_H
+#define SRDWM_EVENT_SYSTEM_H
+
+#include <functional>
+#include <map>
+#include <vector>
+#include <string>
+#include <memory>
+
+// Forward declarations
+class SRDWindow;
+class Monitor;
+
+// Event types
+enum class EventType {
+    WINDOW_CREATED,
+    WINDOW_DESTROYED,
+    WINDOW_MOVED,
+    WINDOW_RESIZED,
+    WINDOW_FOCUSED,
+    WINDOW_UNFOCUSED,
+    WINDOW_MINIMIZED,
+    WINDOW_MAXIMIZED,
+    WINDOW_RESTORED,
+    MONITOR_ADDED,
+    MONITOR_REMOVED,
+    MONITOR_CHANGED,
+    KEY_PRESSED,
+    KEY_RELEASED,
+    MOUSE_MOVED,
+    MOUSE_PRESSED,
+    MOUSE_RELEASED,
+    MOUSE_WHEEL,
+    CUSTOM_EVENT
+};
+
+// Base event class
+class Event {
+public:
+    virtual ~Event() = default;
+    EventType type;
+    
+    Event(EventType t) : type(t) {}
+};
+
+// SRDWindow events
+class SRDWindowEvent : public Event {
+public:
+    SRDWindow* window;
+    
+    SRDWindowEvent(EventType t, SRDWindow* w) : Event(t), window(w) {}
+};
+
+class SRDWindowCreatedEvent : public SRDWindowEvent {
+public:
+    SRDWindowCreatedEvent(SRDWindow* w) : SRDWindowEvent(EventType::WINDOW_CREATED, w) {}
+};
+
+class SRDWindowDestroyedEvent : public SRDWindowEvent {
+public:
+    SRDWindowDestroyedEvent(SRDWindow* w) : SRDWindowEvent(EventType::WINDOW_DESTROYED, w) {}
+};
+
+class SRDWindowMovedEvent : public SRDWindowEvent {
+public:
+    int x, y;
+    
+    SRDWindowMovedEvent(SRDWindow* w, int new_x, int new_y) 
+        : SRDWindowEvent(EventType::WINDOW_MOVED, w), x(new_x), y(new_y) {}
+};
+
+class SRDWindowResizedEvent : public SRDWindowEvent {
+public:
+    int width, height;
+    
+    SRDWindowResizedEvent(SRDWindow* w, int new_width, int new_height) 
+        : SRDWindowEvent(EventType::WINDOW_RESIZED, w), width(new_width), height(new_height) {}
+};
+
+// Input events
+class KeyEvent : public Event {
+public:
+    unsigned int keycode;
+    unsigned int modifiers;
+    
+    KeyEvent(EventType t, unsigned int kc, unsigned int mods) 
+        : Event(t), keycode(kc), modifiers(mods) {}
+};
+
+class MouseEvent : public Event {
+public:
+    int x, y;
+    unsigned int button;
+    unsigned int modifiers;
+    
+    MouseEvent(EventType t, int mouse_x, int mouse_y, unsigned int btn, unsigned int mods) 
+        : Event(t), x(mouse_x), y(mouse_y), button(btn), modifiers(mods) {}
+};
+
+// Event handler function type
+using EventHandler = std::function<void(const Event&)>;
+
+// Event system class
+class EventSystem {
+public:
+    EventSystem();
+    ~EventSystem();
+    
+    // Register event handlers
+    void register_handler(EventType type, EventHandler handler);
+    void unregister_handler(EventType type, EventHandler handler);
+    
+    // Emit events
+    void emit_event(const Event& event);
+    void emit_window_event(EventType type, SRDWindow* window);
+    void emit_key_event(EventType type, unsigned int keycode, unsigned int modifiers);
+    void emit_mouse_event(EventType type, int x, int y, unsigned int button, unsigned int modifiers);
+    
+    // Process event queue
+    void process_events();
+    
+    // Clear all handlers
+    void clear_handlers();
+
+private:
+    std::map<EventType, std::vector<EventHandler>> handlers;
+    std::vector<std::unique_ptr<Event>> event_queue;
+    bool processing_events;
+};
+
+// Global event system instance
+extern EventSystem g_event_system;
+
+#endif // SRDWM_EVENT_SYSTEM_H