feat(effects): implement window rounded corners via scenefx

- Parse effects.windows.rounded/rounding from Lua config
- Add CfgEffectsWindows and CfgEffects structs to Config
- Switch to fx_renderer_create for scenefx support
- Replace 5 wlr/types/wlr_scene.h includes with scenefx variant
- Add config_get_corner_radius() helper (light=6px, heavy=14px)
- Apply corner_radii_top/bottom/left/right to 4 border rects
- Apply wlr_scene_buffer_set_corner_radius to surface buffers
- Disable on fullscreen, restore on exit
- Re-apply on resize and config hot-reload
- Add -Wno-extra-semi for scenefx header compatibility
- All targets compile cleanly (make test passes)

parser/parser.h

@@ -104,6 +104,17 @@ typedef struct {
 	char cmd[CFG_MAX_AUTOSTART_CMD];
 } CfgAutostart;
 
+/* Effects */
+
+typedef struct {
+	bool         rounded;
+	char         rounding[CFG_MAX_STRLEN];
+} CfgEffectsWindows;
+
+typedef struct {
+	CfgEffectsWindows windows;
+} CfgEffects;
+
 /* the whole shebang */
 
 typedef struct {
@@ -135,6 +146,8 @@ typedef struct {
 
 	/* Per-workspace (tag) default layouts, indexed by tag index 0-8 */
 	char workspace_layouts[9][CFG_MAX_STRLEN];
+
+	CfgEffects    effects;
 } Config;
 
 /* Public API */