Show size and a draft indicator in snippet-library rows

src/core/snippet.ts

@@ -121,3 +121,29 @@ export function createSnippet(options: CreateSnippetOptions = {}): Snippet {
 export function hasUnpublishedChanges(snippet: Snippet): boolean {
   return snippet.draftSpec !== snippet.spec;
 }
+
+/**
+ * Approximate payload size of a snippet, in bytes (spec §09 `size`). Measured on
+ * the working draft — the version the editor and preview currently show — as its
+ * UTF-8 byte length, so the figure tracks what the user is actually editing.
+ * `TextEncoder` is a platform global (like `crypto.randomUUID` above), not a
+ * browser/DOM API, so it stays within the portable core.
+ */
+export function snippetSizeBytes(snippet: Snippet): number {
+  return new TextEncoder().encode(snippet.draftSpec).length;
+}
+
+/** Below this we omit the size in the library to reduce clutter (spec §02). */
+const SIZE_DISPLAY_THRESHOLD = 1024;
+
+/**
+ * Human-readable size for the library row, or `null` when the snippet is small
+ * enough that the spec says to omit it (under ~1 KB). Rounded to whole KB/MB —
+ * a list hint, not a precise measure.
+ */
+export function formatSnippetSize(bytes: number): string | null {
+  if (bytes < SIZE_DISPLAY_THRESHOLD) return null;
+  const kb = bytes / 1024;
+  if (kb < 1024) return `${Math.round(kb)} KB`;
+  return `${Math.round(kb / 1024)} MB`;
+}