fix: serve like/repost posts as Note for AP content negotiation

Returning a bare Like/Announce activity breaks Mastodon's
authorize_interaction flow because it expects a content object
(Note/Article). Serve as Note with emoji + linked URL instead.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/jf2-to-as2.js

@@ -52,20 +52,38 @@ export function jf2ToActivityStreams(properties, actorUrl, publicationUrl) {
   const postType = properties["post-type"];
 
   if (postType === "like") {
+    // Serve like posts as Note objects for AP content negotiation.
+    // Returning a bare Like activity breaks Mastodon's authorize_interaction
+    // flow because it expects a content object (Note/Article), not an activity.
+    const likeOf = properties["like-of"];
+    const postUrl = resolvePostUrl(properties.url, publicationUrl);
     return {
       "@context": "https://www.w3.org/ns/activitystreams",
-      type: "Like",
-      actor: actorUrl,
-      object: properties["like-of"],
+      type: "Note",
+      id: postUrl,
+      attributedTo: actorUrl,
+      published: properties.published,
+      url: postUrl,
+      to: ["https://www.w3.org/ns/activitystreams#Public"],
+      cc: [`${actorUrl.replace(/\/$/, "")}/followers`],
+      content: `\u2764\uFE0F <a href="${likeOf}">${likeOf}</a>`,
     };
   }
 
   if (postType === "repost") {
+    // Same rationale as like — serve as Note for content negotiation.
+    const repostOf = properties["repost-of"];
+    const postUrl = resolvePostUrl(properties.url, publicationUrl);
     return {
       "@context": "https://www.w3.org/ns/activitystreams",
-      type: "Announce",
-      actor: actorUrl,
-      object: properties["repost-of"],
+      type: "Note",
+      id: postUrl,
+      attributedTo: actorUrl,
+      published: properties.published,
+      url: postUrl,
+      to: ["https://www.w3.org/ns/activitystreams#Public"],
+      cc: [`${actorUrl.replace(/\/$/, "")}/followers`],
+      content: `\u{1F501} <a href="${repostOf}">${repostOf}</a>`,
     };
   }