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, 35 insertions, 180 deletions

diff --git a/config/srd/keybindings.lua b/config/srd/keybindings.lua
index e2585b2..5c05b84 100644
--- a/config/srd/keybindings.lua
+++ b/config/srd/keybindings.lua
@@ -1,185 +1,58 @@
 - SRDWM Key Bindings Configuration
-- Define all keyboard shortcuts and their actions
+- Every function called here is part of the real `srd` API implemented in
+- crates/config/src/lib.rs - see docs/DEFAULTS.md for the full reference.
 
 local srd = require("srd")
 
 - Layout switching
-srd.bind("Mod4+1", function() 
+srd.bind("Mod4+1", function()
     srd.layout.set("tiling")
     srd.notify("Layout: Tiling", "info")
 end)
 
-srd.bind("Mod4+2", function() 
+srd.bind("Mod4+2", function()
     srd.layout.set("dynamic")
     srd.notify("Layout: Dynamic", "info")
 end)
 
-srd.bind("Mod4+3", function() 
+srd.bind("Mod4+3", function()
     srd.layout.set("floating")
     srd.notify("Layout: Floating", "info")
 end)
 
-- Window management
-srd.bind("Mod4+q", function() 
-    local window = srd.window.focused()
-    if window then
-        window:close()
-    end
-end)
-
-srd.bind("Mod4+m", function() 
-    local window = srd.window.focused()
-    if window then
-        window:minimize()
-    end
-end)
-
-srd.bind("Mod4+f", function() 
-    local window = srd.window.focused()
-    if window then
-        window:maximize()
-    end
-end)
-
-- Window movement (vim-style)
-srd.bind("Mod4+h", function() 
-    srd.window.focus("left")
-end)
-
-srd.bind("Mod4+j", function() 
-    srd.window.focus("down")
-end)
-
-srd.bind("Mod4+k", function() 
-    srd.window.focus("up")
-end)
-
-srd.bind("Mod4+l", function() 
-    srd.window.focus("right")
-end)
+- Window management (act on the focused window)
+srd.bind("Mod4+q", function() srd.window.close() end)
+srd.bind("Mod4+m", function() srd.window.minimize() end)
+srd.bind("Mod4+f", function() srd.window.maximize() end)
+srd.bind("Mod4+Shift+space", function() srd.window.toggle_floating() end)
 
-- Window resizing
-srd.bind("Mod4+Shift+h", function() 
-    local window = srd.window.focused()
-    if window then
-        local x, y, w, h = window:get_geometry()
-        window:set_geometry(x - 10, y, w + 10, h)
-    end
-end)
-
-srd.bind("Mod4+Shift+j", function() 
-    local window = srd.window.focused()
-    if window then
-        local x, y, w, h = window:get_geometry()
-        window:set_geometry(x, y, w, h + 10)
-    end
-end)
-
-srd.bind("Mod4+Shift+k", function() 
-    local window = srd.window.focused()
-    if window then
-        local x, y, w, h = window:get_geometry()
-        window:set_geometry(x, y - 10, w, h + 10)
-    end
-end)
-
-srd.bind("Mod4+Shift+l", function() 
-    local window = srd.window.focused()
-    if window then
-        local x, y, w, h = window:get_geometry()
-        window:set_geometry(x, y, w + 10, h)
-    end
-end)
+- Window navigation (vim-style directional focus)
+srd.bind("Mod4+h", function() srd.window.focus("left") end)
+srd.bind("Mod4+j", function() srd.window.focus("down") end)
+srd.bind("Mod4+k", function() srd.window.focus("up") end)
+srd.bind("Mod4+l", function() srd.window.focus("right") end)
 
 - Workspace management
-srd.bind("Mod4+Tab", function() 
-    srd.workspace.next()
-end)
+srd.bind("Mod4+Tab", function() srd.workspace.next() end)
+srd.bind("Mod4+Shift+Tab", function() srd.workspace.prev() end)
 
-srd.bind("Mod4+Shift+Tab", function() 
-    srd.workspace.prev()
-end)
-
-- Workspace switching with number keys
-for i = 1, 10 do
-    srd.bind("Mod4+" .. i, function()
-        srd.workspace.switch(i)
-    end)
-    
-    srd.bind("Mod4+Shift+" .. i, function()
-        local window = srd.window.focused()
-        if window then
-            srd.workspace.move_window(window, i)
-        end
-    end)
+- Workspace switching with number keys (0 doubles as "workspace 10")
+for i = 0, 9 do
+    srd.bind("Mod4+" .. i, function() srd.workspace.switch(i) end)
+    srd.bind("Mod4+Shift+" .. i, function() srd.workspace.move_window(i) end)
 end
 
-- Monitor switching
-srd.bind("Mod4+Left", function() 
-    srd.monitor.focus("left")
-end)
-
-srd.bind("Mod4+Right", function() 
-    srd.monitor.focus("right")
-end)
-
-- Window state toggles
-srd.bind("Mod4+Shift+space", function() 
-    local window = srd.window.focused()
-    if window then
-        if window:is_floating() then
-            window:set_tiling()
-        else
-            window:set_floating()
-        end
-    end
-end)
-
-srd.bind("Mod4+Shift+f", function() 
-    local window = srd.window.focused()
-    if window then
-        if window:is_fullscreen() then
-            window:unset_fullscreen()
-        else
-            window:set_fullscreen()
-        end
-    end
-end)
-
 - Quick actions
-srd.bind("Mod4+d", function() 
-    srd.spawn("rofi -show drun")
-end)
-
-srd.bind("Mod4+Return", function() 
-    srd.spawn("alacritty")
-end)
-
-srd.bind("Mod4+r", function() 
-    srd.spawn("rofi -show run")
-end)
-
-srd.bind("Mod4+w", function() 
-    srd.spawn("firefox")
-end)
+srd.bind("Mod4+d", function() srd.spawn("rofi -show drun") end)
+srd.bind("Mod4+Return", function() srd.spawn("alacritty") end)
+srd.bind("Mod4+r", function() srd.spawn("rofi -show run") end)
 
-- System actions
-srd.bind("Mod4+Shift+q", function() 
-    srd.quit()
-end)
+- System
+srd.bind("Mod4+Shift+q", function() srd.quit() end)
 
-srd.bind("Mod4+Shift+r", function() 
-    srd.reload_config()
-end)
-
-srd.bind("Mod4+Shift+l", function() 
-    srd.spawn("i3lock")
-end)
-
-- Custom functions
-function toggle_gaps()
-    local current_gap = srd.get("general.window_gap")
-    if current_gap > 0 then
+- Custom function example: toggle window gaps at runtime
+local function toggle_gaps()
+    if srd.get("general.window_gap") > 0 then
         srd.set("general.window_gap", 0)
         srd.notify("Gaps: Off", "info")
     else
@@ -187,31 +60,13 @@ function toggle_gaps()
         srd.notify("Gaps: On", "info")
     end
 end
-
 srd.bind("Mod4+g", toggle_gaps)
 
-- Volume control
-srd.bind("XF86AudioRaiseVolume", function()
-    srd.spawn("pactl set-sink-volume @DEFAULT_SINK@ +5%")
-end)
-
-srd.bind("XF86AudioLowerVolume", function()
-    srd.spawn("pactl set-sink-volume @DEFAULT_SINK@ -5%")
-end)
+- Media keys
+srd.bind("XF86AudioRaiseVolume", function() srd.spawn("pactl set-sink-volume @DEFAULT_SINK@ +5%") end)
+srd.bind("XF86AudioLowerVolume", function() srd.spawn("pactl set-sink-volume @DEFAULT_SINK@ -5%") end)
+srd.bind("XF86AudioMute", function() srd.spawn("pactl set-sink-mute @DEFAULT_SINK@ toggle") end)
+srd.bind("XF86MonBrightnessUp", function() srd.spawn("brightnessctl set +5%") end)
+srd.bind("XF86MonBrightnessDown", function() srd.spawn("brightnessctl set 5%-") end)
 
-srd.bind("XF86AudioMute", function()
-    srd.spawn("pactl set-sink-mute @DEFAULT_SINK@ toggle")
-end)
-
-- Brightness control
-srd.bind("XF86MonBrightnessUp", function()
-    srd.spawn("brightnessctl set +5%")
-end)
-
-srd.bind("XF86MonBrightnessDown", function()
-    srd.spawn("brightnessctl set 5%-")
-end)
-
-- Print key bindings loaded
 print("Key bindings configuration loaded")
-