feat: linkify URLs and extract @mentions in status creation

Mastodon clients send plain text — the server must convert bare URLs
and @user@domain mentions into HTML links. Previously, URLs appeared
as plain text and mentions were not stored as mention objects.

- Bare URLs (http/https) are wrapped in <a> tags
- @user@domain patterns are converted to profile links with h-card markup
- Mentions are extracted into the mentions[] array with name and URL
- Only processes content that doesn't already contain <a> tags
  (avoids double-linkifying Micropub-rendered content)

lib/mastodon/routes/statuses.js

@@ -247,12 +247,17 @@ router.post("/api/v1/statuses", async (req, res, next) => {
       });
     };
 
+    // Process content: linkify URLs and extract @mentions
+    const rawContent = data.properties.content || { text: statusText || "", html: "" };
+    const processedContent = processStatusContent(rawContent, statusText || "");
+    const mentions = extractMentions(statusText || "");
+
     const now = new Date().toISOString();
     const timelineItem = await addTimelineItem(collections, {
       uid: postUrl,
       url: postUrl,
       type: data.properties["post-type"] || "note",
-      content: data.properties.content || { text: statusText || "", html: "" },
+      content: processedContent,
       summary: spoilerText || "",
       sensitive: sensitive === true || sensitive === "true",
       visibility: visibility || "public",
@@ -274,7 +279,7 @@ router.post("/api/v1/statuses", async (req, res, next) => {
       category: categories,
       counts: { replies: 0, boosts: 0, likes: 0 },
       linkPreviews: [],
-      mentions: [],
+      mentions,
       emojis: [],
     });
 
@@ -636,4 +641,68 @@ async function loadItemInteractions(collections, item) {
   return { favouritedIds, rebloggedIds, bookmarkedIds };
 }
 
+/**
+ * Process status content: linkify bare URLs and convert @mentions to links.
+ *
+ * Mastodon clients send plain text — the server is responsible for
+ * converting URLs and mentions into HTML links.
+ *
+ * @param {object} content - { text, html } from Micropub pipeline
+ * @param {string} rawText - Original status text from client
+ * @returns {object} { text, html } with linkified content
+ */
+function processStatusContent(content, rawText) {
+  let html = content.html || content.text || rawText || "";
+
+  // If the HTML is just plain text wrapped in <p>, process it
+  // Don't touch HTML that already has links (from Micropub rendering)
+  if (!html.includes("<a ")) {
+    // Linkify bare URLs (http/https)
+    html = html.replace(
+      /(https?:\/\/[^\s<>"')\]]+)/g,
+      '<a href="$1" rel="nofollow noopener noreferrer" target="_blank">$1</a>',
+    );
+
+    // Convert @user@domain mentions to profile links
+    html = html.replace(
+      /(?:^|\s)(@([a-zA-Z0-9_]+)@([a-zA-Z0-9.-]+\.[a-zA-Z]{2,}))/g,
+      (match, full, username, domain) =>
+        match.replace(
+          full,
+          `<span class="h-card"><a href="https://${domain}/@${username}" class="u-url mention" rel="nofollow noopener noreferrer" target="_blank">@${username}@${domain}</a></span>`,
+        ),
+    );
+  }
+
+  return {
+    text: content.text || rawText || "",
+    html,
+  };
+}
+
+/**
+ * Extract @user@domain mentions from text into mention objects.
+ *
+ * @param {string} text - Status text
+ * @returns {Array<{name: string, url: string}>} Mention objects
+ */
+function extractMentions(text) {
+  if (!text) return [];
+  const mentionRegex = /@([a-zA-Z0-9_]+)@([a-zA-Z0-9.-]+\.[a-zA-Z]{2,})/g;
+  const mentions = [];
+  const seen = new Set();
+  let match;
+  while ((match = mentionRegex.exec(text)) !== null) {
+    const [, username, domain] = match;
+    const key = `${username}@${domain}`.toLowerCase();
+    if (seen.has(key)) continue;
+    seen.add(key);
+    mentions.push({
+      name: `@${username}@${domain}`,
+      url: `https://${domain}/@${username}`,
+    });
+  }
+  return mentions;
+}
+
 export default router;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@rmdes/indiekit-endpoint-activitypub",
-  "version": "3.7.2",
+  "version": "3.7.3",
   "description": "ActivityPub federation endpoint for Indiekit via Fedify. Adds full fediverse support: actor, inbox, outbox, followers, following, syndication, and Mastodon migration.",
   "keywords": [
     "indiekit",