feat: the extension adds Discord channels to an artist you pick, and its tests gate the XPI (milestone 429)

Server (#4420)
- extension_service gains a Discord pattern (server or channel, jump links,
  ptb/canary; not DMs or threads), mirrored in platforms.js and pinned by
  the shared artist-url-samples.json.
- probe on a Discord URL matches the source by ids under any artist, reports
  a whole-server source as covering the channel, suggests the artist who owns
  another source on the same server, and names server/channel via the stored
  token (best-effort, bounded, no rate-limit waits).
- quick-add takes artist_id / artist_name; Discord URLs are stored canonical.

Extension (#4421, #4422)
- Content script on discord.com; SPA navigation by URL polling (the old
  pushState patch ran in the isolated world and never fired); stale probes
  are dropped.
- Discord chip opens an Add panel: this channel or the whole server, and the
  suggested artist / a search / a new name.
- Popup: sources show artist, platform and state; a Discord token export is
  verified by FC and the result shown. Token capture covers ptb/canary.
- Pure logic in lib/chip.js and lib/popup-format.js, with specs.

CI (#4423)
- extension.yml's lane (web-ext lint, vitest, XPI contents) moves into
  build.yml as extension-test and joins the needs of sign-extension,
  build-web and build-agent. As a separate workflow it gated nothing: a red
  extension suite still signed and shipped the XPI (rule 177).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR

extension/popup/popup.html

@@ -47,6 +47,7 @@
   </section>
 
   <script src="../lib/platforms.js"></script>
+  <script src="../lib/popup-format.js"></script>
   <script src="popup.js"></script>
 </body>
 </html>

extension/popup/popup.js

@@ -159,7 +159,11 @@ async function exportPlatformCookies(key, card) {
   try {
     const r = await browser.runtime.sendMessage({ type: 'EXPORT_COOKIES', platform: key });
     if (r.error) showError(r.error);
-    else {
+    else if (key === 'discord') {
+      const m = tokenExportMessage(r.verify);
+      showStatusMessage(m.text, m.kind);
+      await loadPlatformStatus();
+    } else {
       const n = r.cookieCount ?? null;
       const verifiedSuffix = r.verified ? ' (verified ✓)' : '';
       const msg = n !== null
@@ -205,7 +209,10 @@ async function loadSources() {
     c.appendChild(mutedNote('No sources yet.'));
     return;
   }
-  for (const src of r.sources) c.appendChild(createSourceRow(src));
+  // Grouped by artist so a creator's Patreon and Discord sit together.
+  const sorted = [...r.sources].sort((a, b) =>
+    (a.artist_name || '').localeCompare(b.artist_name || '') || a.id - b.id);
+  for (const src of sorted) c.appendChild(createSourceRow(src));
 }
 
 function createSourceRow(src) {
@@ -215,11 +222,16 @@ function createSourceRow(src) {
   info.className = 'info';
   const name = document.createElement('div');
   name.className = 'name';
-  name.textContent = `${src.platform} · #${src.id}`;
+  const platformName = PLATFORMS[src.platform]?.name || src.platform;
+  name.textContent = `${src.artist_name || `Source #${src.id}`} · ${platformName}`;
+  const state = sourceStatus(src);
+  const st = document.createElement('div');
+  st.className = `status ${state.kind}`;
+  st.textContent = state.text;
   const url = document.createElement('div');
   url.className = 'url';
   url.textContent = src.url;
-  info.appendChild(name); info.appendChild(url);
+  info.appendChild(name); info.appendChild(st); info.appendChild(url);
   const play = document.createElement('button');
   play.className = 'play';
   play.textContent = '▶';
@@ -229,7 +241,7 @@ function createSourceRow(src) {
     const r = await browser.runtime.sendMessage({ type: 'CHECK_SOURCE', sourceId: src.id });
     play.disabled = false;
     if (r.error) showError(r.error);
-    else showSuccess(`Triggered check for source #${src.id}`);
+    else showSuccess(`Check queued for ${src.artist_name || `source #${src.id}`} (${platformName})`);
   });
   row.appendChild(info); row.appendChild(play);
   return row;