fix: chat accepts quotes now

lib/post-share-text.ts

@@ -0,0 +1,53 @@
+/**
+ * Builds the shareable text for a post — the caption, its source reference,
+ * and a link.
+ *
+ * Extracted so the native share sheet and "send to a chat" quote a post
+ * identically. They differ only in where the text ends up, and two copies of
+ * this would drift the moment either format changed.
+ */
+
+import { createShortLink } from "@/lib/share";
+import { structuredReferenceForPost } from "@/lib/source-reference";
+import type { Post } from "@/lib/social";
+
+export type PostShareText = {
+  /** Short link when the shortener answered, canonical URL otherwise. */
+  url: string;
+  /** Source reference on one line, for a native share sheet's title slot. */
+  title: string;
+  /** Caption, source reference and link — the body of the share. */
+  text: string;
+};
+
+/**
+ * `viewerHandle` covers the case where the BFF's create response omits
+ * author_handle: the poster IS the signed-in user right after posting.
+ * Returns null when neither yields a handle, since there is no post URL
+ * without one.
+ */
+export async function buildPostShareText(
+  post: Post,
+  viewerHandle: string | undefined,
+): Promise<PostShareText | null> {
+  const handle = post.author_handle ?? viewerHandle ?? "";
+  if (!handle) return null;
+
+  const longPath = `/u/${encodeURIComponent(handle)}/posts#post-${post.id}`;
+  const code = await createShortLink(longPath);
+  const origin = window.location.origin;
+  const url = code
+    ? new URL(`/share/${code}`, origin).toString()
+    : new URL(longPath, origin).toString();
+
+  const ref = structuredReferenceForPost(post.source_url, post.source_title);
+  const lines = [`“${post.caption}”`, "", "Source:", ref.title];
+  if (ref.detail) lines.push(ref.detail);
+  lines.push(url);
+
+  return {
+    url,
+    title: ref.detail ? `${ref.title} — ${ref.detail}` : ref.title,
+    text: lines.join("\n"),
+  };
+}