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, 140 insertions, 0 deletions

diff --git a/legacy-cpp/src/platform/windows_platform.h b/legacy-cpp/src/platform/windows_platform.h
new file mode 100644
index 0000000..70b7d54
--- /dev/null
+++ b/legacy-cpp/src/platform/windows_platform.h
@@ -0,0 +1,140 @@
+#ifndef SRDWM_WINDOWS_PLATFORM_H
+#define SRDWM_WINDOWS_PLATFORM_H
+
+#include "platform.h"
+#include <windows.h>
+#include <memory>
+#include <string>
+#include <map>
+
+class SRDWindowsPlatform : public Platform {
+public:
+    SRDWindowsPlatform();
+    ~SRDWindowsPlatform() 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 (SRDWindows 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;
+
+    // Windows-specific features
+    void enable_dwm_composition(bool enabled);
+    void set_dwm_window_attribute(HWND hwnd, DWORD attribute, DWORD value);
+    void set_dwm_window_thumbnail(HWND hwnd, HWND thumbnail_hwnd);
+    void set_dwm_window_peek(HWND hwnd, bool enabled);
+    
+    // Virtual Desktop support (Windows 10+)
+    void create_virtual_desktop();
+    void remove_virtual_desktop(int desktop_id);
+    void switch_to_virtual_desktop(int desktop_id);
+    int get_current_virtual_desktop() const;
+    std::vector<int> get_virtual_desktops() const;
+    void move_window_to_desktop(SRDWindow* window, int desktop_id);
+    
+    // Taskbar integration
+    void set_taskbar_visible(bool visible);
+    void set_taskbar_position(int position); // 0=bottom, 1=top, 2=left, 3=right
+    void set_taskbar_auto_hide(bool enabled);
+    void update_taskbar_preview(HWND hwnd, const std::string& title);
+    
+    // Aero effects
+    void enable_aero_effects(bool enabled);
+    void set_window_transparency(HWND hwnd, BYTE alpha);
+    void set_window_blur(HWND hwnd, bool enabled);
+    void set_window_shadow(HWND hwnd, bool enabled);
+    
+    // System tray integration
+    void add_system_tray_icon(const std::string& tooltip, HICON icon);
+    void remove_system_tray_icon();
+    void show_system_tray_menu(HMENU menu);
+
+    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_;
+    HINSTANCE h_instance_;
+    std::map<HWND, SRDWindow*> window_map_;
+    std::vector<Monitor> monitors_;
+    
+    // Decoration state
+    bool decorations_enabled_;
+    int border_width_;
+    COLORREF border_color_;
+    COLORREF focused_border_color_;
+    
+    // Windows-specific state
+    bool dwm_enabled_;
+    bool aero_enabled_;
+    bool taskbar_visible_;
+    bool taskbar_auto_hide_;
+    int taskbar_position_;
+    int current_virtual_desktop_;
+    std::vector<int> virtual_desktops_;
+    NOTIFYICONDATA system_tray_icon_;
+    
+    // SRDWindow class registration
+    bool register_window_class();
+    void unregister_window_class();
+    
+    // SRDWindow procedure
+    static LRESULT CALLBACK window_proc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam);
+    
+    // Event conversion
+    void convert_win32_message(UINT msg, WPARAM wparam, LPARAM lparam, std::vector<Event>& events);
+    
+    // Monitor enumeration
+    static BOOL CALLBACK enum_monitor_proc(HMONITOR hmonitor, HDC hdc_monitor, LPRECT lprc_monitor, LPARAM dw_data);
+    
+    // Utility methods
+    void update_monitors();
+    SRDWindow* find_window_by_hwnd(HWND hwnd);
+    
+    // Decoration methods
+    void apply_dwm_border_color(HWND hwnd, int r, int g, int b);
+    void remove_dwm_border_color(HWND hwnd);
+    
+    // Virtual Desktop methods
+    void initialize_virtual_desktops();
+    void cleanup_virtual_desktops();
+    
+    // DWM methods
+    bool initialize_dwm();
+    void cleanup_dwm();
+    
+    // Taskbar methods
+    void initialize_taskbar();
+    void update_taskbar();
+};
+
+#endif // SRDWM_WINDOWS_PLATFORM_H
+