fix: add to/cc addressing to Like and Announce activities

Mastodon shared inboxes require cc:followers to route activities to
local followers. Like had no to/cc at all, Announce was missing cc.
Also normalize nested tags (on/art/music → music) in hashtag names.

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

lib/jf2-to-as2.js

@@ -250,9 +250,12 @@ export function jf2ToAS2Activity(properties, actorUrl, publicationUrl, options =
   if (postType === "like") {
     const likeOf = properties["like-of"];
     if (!likeOf) return null;
+    const followersUrl = `${actorUrl.replace(/\/$/, "")}/followers`;
     return new Like({
       actor: actorUri,
       object: new URL(likeOf),
+      to: new URL("https://www.w3.org/ns/activitystreams#Public"),
+      cc: new URL(followersUrl),
     });
   }
 
@@ -260,10 +263,12 @@ export function jf2ToAS2Activity(properties, actorUrl, publicationUrl, options =
   if (postType === "repost") {
     const repostOf = properties["repost-of"];
     if (!repostOf) return null;
+    const followersUrl = `${actorUrl.replace(/\/$/, "")}/followers`;
     return new Announce({
       actor: actorUri,
       object: new URL(repostOf),
       to: new URL("https://www.w3.org/ns/activitystreams#Public"),
+      cc: new URL(followersUrl),
     });
   }
 
@@ -554,7 +559,7 @@ function buildPlainTags(properties, publicationUrl, existing) {
     for (const cat of asArray(properties.category)) {
       tags.push({
         type: "Hashtag",
-        name: `#${cat.replace(/\s+/g, "")}`,
+        name: `#${cat.split("/").at(-1).replace(/\s+/g, "")}`,
         href: `${publicationUrl}categories/${encodeURIComponent(cat)}`,
       });
     }
@@ -576,7 +581,7 @@ function buildFedifyTags(properties, publicationUrl, postType) {
     for (const cat of asArray(properties.category)) {
       tags.push(
         new Hashtag({
-          name: `#${cat.replace(/\s+/g, "")}`,
+          name: `#${cat.split("/").at(-1).replace(/\s+/g, "")}`,
           href: new URL(
             `${publicationUrl}categories/${encodeURIComponent(cat)}`,
           ),