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, 82 insertions, 0 deletions

diff --git a/legacy-cpp/src/core/window.cc b/legacy-cpp/src/core/window.cc
new file mode 100644
index 0000000..cefc131
--- /dev/null
+++ b/legacy-cpp/src/core/window.cc
@@ -0,0 +1,82 @@
+#include "window.h"
+
+SRDWindow::SRDWindow(int id, const std::string& title)
+    : id_(id), title_(title), x_(0), y_(0), width_(0), height_(0), decorated_(true) {
+}
+
+int SRDWindow::getId() const {
+    return id_;
+}
+
+const std::string& SRDWindow::getTitle() const {
+    return title_;
+}
+
+int SRDWindow::getX() const {
+    return x_;
+}
+
+int SRDWindow::getY() const {
+    return y_;
+}
+
+int SRDWindow::getWidth() const {
+    return width_;
+}
+
+int SRDWindow::getHeight() const {
+    return height_;
+}
+
+bool SRDWindow::isDecorated() const {
+    return decorated_;
+}
+
+void SRDWindow::setPosition(int x, int y) {
+    x_ = x;
+    y_ = y;
+}
+
+void SRDWindow::setSize(int width, int height) {
+    width_ = width;
+    height_ = height;
+}
+
+void SRDWindow::setGeometry(int x, int y, int width, int height) {
+    x_ = x;
+    y_ = y;
+    width_ = width;
+    height_ = height;
+}
+
+void SRDWindow::setDimensions(int x, int y, int width, int height) {
+    x_ = x;
+    y_ = y;
+    width_ = width;
+    height_ = height;
+}
+
+void SRDWindow::setDecorated(bool decorated) {
+    decorated_ = decorated;
+}
+
+void SRDWindow::setId(int id) {
+    id_ = id;
+}
+
+// Basic methods for managing window state (will be platform-specific)
+void SRDWindow::map() {
+    // Platform-specific implementation to show the window
+}
+
+void SRDWindow::unmap() {
+    // Platform-specific implementation to hide the window
+}
+
+void SRDWindow::focus() {
+    // Platform-specific implementation to give focus to the window
+}
+
+void SRDWindow::close() {
+    // Platform-specific implementation to close the window
+}