bug fixes, and performance improvements, and drawer

utils/topic-sync.ts

@@ -0,0 +1,21 @@
+/** Stable across database Dates, JSON SSE payloads, and Nuxt hydration. */
+export const serializeTopicSnapshot = (topic: unknown): string => JSON.stringify(topic, (_key, value) => {
+    if (value === null || typeof value !== 'object' || Array.isArray(value)) {
+        return value;
+    }
+
+    return Object.fromEntries(Object.keys(value).sort().map(key => [key, value[key]]));
+});
+
+/** Absolute offsets make replay across a snapshot boundary idempotent. */
+export const appendTextDelta = (current: string, content: string, offset?: number): string => {
+    if (offset === undefined) {
+        return current + content;
+    }
+    if (offset > current.length) {
+        // A gap requires reconciliation, not silently concatenating corrupt text.
+        return current;
+    }
+    const overlap = current.length - offset;
+    return overlap >= content.length ? current : current + content.slice(overlap);
+};