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, 36 insertions, 0 deletions

diff --git a/legacy-cpp/src/input/input_handler.h b/legacy-cpp/src/input/input_handler.h
new file mode 100644
index 0000000..2f35608
--- /dev/null
+++ b/legacy-cpp/src/input/input_handler.h
@@ -0,0 +1,36 @@
+#ifndef SRDWM_INPUT_HANDLER_H
+#define SRDWM_INPUT_HANDLER_H
+
+#include <memory>
+
+// Define basic event structures (these will need more detail later)
+struct KeyboardEvent {
+    int key_code;
+    // Add modifiers, state (press/release)
+};
+
+struct MouseEvent {
+    enum class Type { Press, Release, Motion };
+    Type type;
+    int button; // Valid for Press/Release
+    int x, y;
+    // Add modifiers
+};
+
+class InputHandler {
+public:
+    virtual ~InputHandler() = default;
+
+    // Pure virtual methods for handling events
+    virtual void handle_key_press(const KeyboardEvent& event) = 0;
+    virtual void handle_key_release(const KeyboardEvent& event) = 0;
+    virtual void handle_mouse_button_press(const MouseEvent& event) = 0;
+    virtual void handle_mouse_button_release(const MouseEvent& event) = 0;
+    virtual void handle_mouse_motion(const MouseEvent& event) = 0;
+
+    // Other potential input-related methods
+    // virtual void initialize() = 0;
+    // virtual void shutdown() = 0;
+};
+
+#endif // SRDWM_INPUT_HANDLER_H