feat(webseed): upload form accepts multiple web seeds (slice 2/3)

Let uploaders declare a backup origin at creation time so the swarm can keep
streaming when the primary CDN is overloaded.

- upload-modal.html: the single "Web Seed (ws)" input becomes a "Web seeds
  (one per line)" textarea with help text explaining the backup-origin use
  case and the byte-identical-file requirement.
- UploadModal: in upload mode the R2/CDN url stays the primary webseed and any
  textarea entries follow it (passed as [primaryUrl, textarea]); external mode
  already flowed the field through. All parsing stays in the payload layer.
- videoNotePayload.normalizeWebSeedList now splits every entry (array OR
  string) on newlines/commas, so the upload-modal's [url, "a\nb"] shape and a
  plain multi-line string both expand + dedupe correctly.

Mutation-verified (array entries no longer split fails the upload-shape test);
build + full unit suite green. Lints relevant to the change (inline-styles,
tokens, innerHTML) pass.

Note: npm run lint also reports pre-existing file-size violations in unrelated
files (SignerManager, watchHistory, playbackService, webtorrent, etc.) that
grew in earlier commits — none are touched here. Flagging separately.

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

components/upload-modal.html

@@ -376,8 +376,9 @@
                      <!-- Additional Technical Sections (Web Seeds, etc) -->
                      <div class="grid gap-3 md:grid-cols-2">
                          <div class="space-y-2">
-                             <label class="block text-xs font-medium text-muted-strong">Web Seed (ws)</label>
-                             <input id="input-ws" type="url" class="input text-sm" placeholder="https://..." />
+                             <label class="block text-xs font-medium text-muted-strong">Web seeds (one per line)</label>
+                             <textarea id="input-ws" rows="2" class="textarea text-sm" placeholder="https://cdn.example.com/video.mp4&#10;https://backup.example.com/video.mp4"></textarea>
+                             <p class="text-xs text-muted">Add a backup origin so the swarm can keep streaming if the primary is overloaded. Each must serve the exact same file.</p>
                          </div>
                           <div class="space-y-2">
                              <label class="block text-xs font-medium text-muted-strong">Torrent File (xs)</label>

js/services/videoNotePayload.js

@@ -47,25 +47,30 @@ function normalizeString(value) {
 function normalizeWebSeedList(value) {
   const out = [];
   const seen = new Set();
+  // Each entry may itself carry several URLs separated by newlines/commas (a
+  // textarea field), so split every entry regardless of whether the caller
+  // passed an array or a single string.
   const push = (entry) => {
     if (typeof entry !== "string") {
       return;
     }
-    const trimmed = entry.trim();
-    if (!trimmed) {
-      return;
+    for (const piece of entry.split(/[\r\n,]+/)) {
+      const trimmed = piece.trim();
+      if (!trimmed) {
+        continue;
+      }
+      const key = trimmed.toLowerCase();
+      if (seen.has(key)) {
+        continue;
+      }
+      seen.add(key);
+      out.push(trimmed);
     }
-    const key = trimmed.toLowerCase();
-    if (seen.has(key)) {
-      return;
-    }
-    seen.add(key);
-    out.push(trimmed);
   };
   if (Array.isArray(value)) {
     value.forEach(push);
   } else if (typeof value === "string") {
-    value.split(/[\r\n,]+/).forEach(push);
+    push(value);
   }
   return out;
 }

js/ui/components/UploadModal.js

@@ -1073,7 +1073,13 @@ export class UploadModal {
              metadata.storagePointer =
                  this.videoUploadState.storagePointer ||
                  deriveStoragePointerFromUrl(metadata.url, providerLabel);
-             metadata.ws = this.videoUploadState.url; // WebSeed is same as R2 URL
+             // The R2/CDN url is the primary webseed; any additional backup
+             // webseeds the uploader entered (one per line) follow it.
+             // normalizeVideoNotePayload splits + dedupes this list.
+             metadata.ws = [
+               this.videoUploadState.url,
+               this.inputs.ws?.value || "",
+             ];
              metadata.xs = this.torrentState.url || "";
 
              // NIP-71 IMETA for the main video

tests/multi-webseed.test.mjs

@@ -81,6 +81,25 @@ test("a single webseed string still works (back-compat)", () => {
   assert.equal(payload.legacyFormData.ws, SEED_A);
 });
 
+test("upload-modal shape ([primaryUrl, textarea]) yields primary-first, all split", () => {
+  // This mirrors exactly what UploadModal hands over in upload mode: the CDN
+  // url as the primary entry, followed by the raw multi-line textarea value.
+  const cdn = "https://cdn.example.com/video.mp4";
+  const { payload } = normalizeVideoNotePayload({
+    title: "Upload shape",
+    url: cdn,
+    magnet: MAGNET,
+    ws: [cdn, `${SEED_A}\n${SEED_B}`],
+  });
+
+  const seeds = extractAllWebSeeds(payload.legacyFormData.magnet);
+  assert.ok(seeds.includes(cdn), "CDN url carried");
+  assert.ok(seeds.includes(SEED_A), "first backup webseed carried");
+  assert.ok(seeds.includes(SEED_B), "second backup webseed carried");
+  // CDN stays the primary (first) seed.
+  assert.equal(payload.legacyFormData.ws, cdn);
+});
+
 test("duplicate webseeds are not written twice", () => {
   const { payload } = normalizeVideoNotePayload({
     title: "Dupe seed",