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, 94 insertions, 0 deletions

diff --git a/legacy-cpp/src/core/event_system.cc b/legacy-cpp/src/core/event_system.cc
new file mode 100644
index 0000000..ed022cb
--- /dev/null
+++ b/legacy-cpp/src/core/event_system.cc
@@ -0,0 +1,94 @@
+#include "event_system.h"
+#include "window.h"
+#include <iostream>
+#include <algorithm>
+
+// Global event system instance
+EventSystem g_event_system;
+
+EventSystem::EventSystem() : processing_events(false) {
+}
+
+EventSystem::~EventSystem() {
+    clear_handlers();
+}
+
+void EventSystem::register_handler(EventType type, EventHandler handler) {
+    handlers[type].push_back(handler);
+}
+
+void EventSystem::unregister_handler(EventType type, EventHandler handler) {
+    auto& type_handlers = handlers[type];
+    type_handlers.erase(
+        std::remove_if(type_handlers.begin(), type_handlers.end(),
+            [&handler](const EventHandler& h) {
+                // Note: This is a simplified comparison
+                // In a real implementation, you'd want a more sophisticated way to identify handlers
+                return false; // For now, we don't remove handlers
+            }),
+        type_handlers.end()
+    );
+}
+
+void EventSystem::emit_event(const Event& event) {
+    if (processing_events) {
+        // Queue the event if we're currently processing events
+        event_queue.push_back(std::make_unique<Event>(event));
+        return;
+    }
+    
+    auto it = handlers.find(event.type);
+    if (it != handlers.end()) {
+        for (const auto& handler : it->second) {
+            try {
+                handler(event);
+            } catch (const std::exception& e) {
+                std::cerr << "Error in event handler: " << e.what() << std::endl;
+            }
+        }
+    }
+}
+
+void EventSystem::emit_window_event(EventType type, SRDWindow* window) {
+    switch (type) {
+        case EventType::WINDOW_CREATED:
+            emit_event(SRDWindowCreatedEvent(window));
+            break;
+        case EventType::WINDOW_DESTROYED:
+            emit_event(SRDWindowDestroyedEvent(window));
+            break;
+        default:
+            // For other window events, we need more context
+            break;
+    }
+}
+
+void EventSystem::emit_key_event(EventType type, unsigned int keycode, unsigned int modifiers) {
+    emit_event(KeyEvent(type, keycode, modifiers));
+}
+
+void EventSystem::emit_mouse_event(EventType type, int x, int y, unsigned int button, unsigned int modifiers) {
+    emit_event(MouseEvent(type, x, y, button, modifiers));
+}
+
+void EventSystem::process_events() {
+    if (processing_events) {
+        return; // Prevent recursive processing
+    }
+    
+    processing_events = true;
+    
+    // Process queued events
+    while (!event_queue.empty()) {
+        auto event = std::move(event_queue.front());
+        event_queue.erase(event_queue.begin());
+        
+        emit_event(*event);
+    }
+    
+    processing_events = false;
+}
+
+void EventSystem::clear_handlers() {
+    handlers.clear();
+}