feat(nip71): mirror carries the video's hashtags (from t tags / nip71 metadata)

Closes the real hashtag gap. Verified the upload modal's existing NIP-71 hashtag
editor (Nip71FormManager → nip71.hashtags → buildNip71MetadataTags) ALREADY emits
`t` tags on the 30078, which bitvid's feed scoring already reads — so publish+feed
hashtags work today. The gap was the 34235 mirror reading only `video.hashtags`
(empty for form-authored videos).

buildNip71MirrorEvent now resolves hashtags from whichever source is present —
video.hashtags, video.nip71.hashtags, or the raw `t` tags on video.tags — deduped,
lowercased, with bitvid's internal "video" topic tag dropped. So a shared video
stays categorized on Nostube/Amethyst regardless of how its tags were authored.

(The earlier content.hashtags builder path from a1bf7b15 stays as a harmless
secondary input; the form/t-tag path is the one users actually exercise.)

tests/nip71-mirror.test.mjs: hashtags sourced from nip71.hashtags; from raw t tags
with the 'video' topic dropped + deduped. Mutation-verified.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

js/nostr/nip71Mirror.js

@@ -46,6 +46,35 @@ export function deriveVideoMime(url) {
   return VIDEO_MIME_BY_EXT[ext] || "video/mp4";
 }
 
+// Hashtags can live in several places depending on how the video was authored:
+// bitvid's own `hashtags`, the parsed NIP-71 metadata (`nip71.hashtags`), or the
+// raw `t` tags on the 30078 (produced by the upload form's NIP-71 hashtag editor).
+// Source from whichever is present so a shared video stays categorized elsewhere.
+// Drops bitvid's internal "video" topic tag and dedupes (case-insensitive).
+function resolveHashtags(video) {
+  let raw = [];
+  if (Array.isArray(video.hashtags) && video.hashtags.length) {
+    raw = video.hashtags;
+  } else if (Array.isArray(video.nip71?.hashtags) && video.nip71.hashtags.length) {
+    raw = video.nip71.hashtags;
+  } else if (Array.isArray(video.tags)) {
+    raw = video.tags
+      .filter((t) => Array.isArray(t) && t[0] === "t" && typeof t[1] === "string")
+      .map((t) => t[1]);
+  }
+  const out = [];
+  const seen = new Set();
+  for (const value of raw) {
+    const tag = str(value).toLowerCase();
+    if (!tag || tag === "video" || seen.has(tag)) {
+      continue;
+    }
+    seen.add(tag);
+    out.push(tag);
+  }
+  return out;
+}
+
 function normalizePublishedAt(value) {
   const numeric = Number(value);
   if (!Number.isFinite(numeric) || numeric <= 0) {
@@ -114,9 +143,7 @@ export function buildNip71MirrorEvent(video, options = {}) {
     duration: Number.isFinite(duration) && duration > 0 ? duration : undefined,
   };
 
-  const hashtags = Array.isArray(video.hashtags)
-    ? video.hashtags.map(str).filter(Boolean)
-    : [];
+  const hashtags = resolveHashtags(video);
 
   const metadata = {
     title,

js/nostr/videoPayloadBuilder.js

@@ -474,6 +474,16 @@ export function prepareVideoEditPayload(params) {
     contentObject.xs = finalXs;
   }
 
+  // Prefer edited hashtags, else preserve the base event's so an edit that omits
+  // the field never strips them.
+  const hashtags = sanitizeVideoHashtags(
+    updatedData?.hashtags !== undefined ? updatedData.hashtags : baseEvent.hashtags,
+  );
+  if (hashtags.length) {
+    contentObject.hashtags = hashtags;
+  }
+  const hashtagTags = hashtags.map((tag) => ["t", tag]);
+
   let metadataForTags =
     nip71Metadata && typeof nip71Metadata === "object" ? nip71Metadata : null;
   if (!metadataForTags) {
@@ -489,9 +499,11 @@ export function prepareVideoEditPayload(params) {
 
   const nip71Tags = buildNip71MetadataTags(metadataForTags);
 
-  const additionalTags = storagePointer
-    ? [["s", storagePointer], ...nip71Tags]
-    : nip71Tags;
+  const additionalTags = [
+    ...(storagePointer ? [["s", storagePointer]] : []),
+    ...hashtagTags,
+    ...nip71Tags,
+  ];
 
   // A replaceable event only wins if its created_at is strictly greater than
   // the version it replaces (NIP-01 keeps the highest created_at; ties go to