feat(gamification): emit task-uncompleted + task-deleted events

Phase 8 completionStats store listens on these events to refresh the
daily count. Keeps the badge + sparkline accurate after un-tick / delete
paths, which don't currently fire kon:task-completed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/stores/page.svelte.ts

@@ -445,6 +445,9 @@ export async function deleteTask(id: string) {
     if (idx >= 0) {
       tasks.splice(idx, 1);
       broadcastTasks();
+      if (typeof window !== "undefined") {
+        window.dispatchEvent(new CustomEvent("kon:task-deleted", { detail: { id } }));
+      }
     }
   } catch (err) {
     toasts.error("Couldn't delete task", errorMessage(err));
@@ -474,6 +477,9 @@ export async function uncompleteTask(id: string) {
   try {
     await invoke("uncomplete_task_cmd", { id });
     applyLocalTaskUpdate(id, { done: false, doneAt: null });
+    if (typeof window !== "undefined") {
+      window.dispatchEvent(new CustomEvent("kon:task-uncompleted", { detail: { id } }));
+    }
   } catch (err) {
     toasts.error("Couldn't uncomplete task", errorMessage(err));
   }