window-rules/foreign-toplevel: add per-window <taskbarScope> with 4 visibility modes

Introduce a per-window rule `<taskbarScope>` that controls where a window's
*taskbar entry* appears. This affects taskbar listing only (via foreign-toplevel
output membership); it does not change sticky/omnipresent state, focus, or
workspace membership.

Supported values (case-insensitive):
- here       -> show only when both match: the window's monitor AND its active workspace
- monitor    -> show only on the window's monitor, across that monitor's workspaces
                (default if the key is omitted)
- workspace  -> show on all monitors currently on the window's workspace
- everywhere -> show on all monitors and all workspaces

src/config/rcxml.c

@@ -243,6 +243,32 @@ set_property(const char *str, enum property *variable)
 	*variable = ret ? LAB_PROP_TRUE : LAB_PROP_FALSE;
 }
 
+static void
+set_taskbar_scope(const char *str, enum taskbar_scope *variable)
+{
+	if (!str) {
+		*variable = LAB_TASKBAR_SCOPE_UNSPECIFIED;
+		return;
+	}
+	if (!strcasecmp(str, "here")) {
+		*variable = LAB_TASKBAR_SCOPE_HERE;
+		return;
+	}
+	if (!strcasecmp(str, "monitor")) {
+		*variable = LAB_TASKBAR_SCOPE_MONITOR;
+		return;
+	}
+	if (!strcasecmp(str, "workspace")) {
+		*variable = LAB_TASKBAR_SCOPE_WORKSPACE;
+		return;
+	}
+	if (!strcasecmp(str, "everywhere")) {
+		*variable = LAB_TASKBAR_SCOPE_EVERYWHERE;
+		return;
+	}
+	*variable = LAB_TASKBAR_SCOPE_UNSPECIFIED;
+}
+
 static void
 fill_window_rule(xmlNode *node)
 {
@@ -300,6 +326,8 @@ fill_window_rule(xmlNode *node)
 			set_property(content, &window_rule->ignore_configure_request);
 		} else if (!strcasecmp(key, "fixedPosition")) {
 			set_property(content, &window_rule->fixed_position);
+		} else if (!strcasecmp(key, "taskbarScope")) {
+			set_taskbar_scope(content, &window_rule->scope_taskbar);
 		}
 	}