Add subscription debug panel (Ctrl+Shift+D)

Hidden dev tool showing NDK uptime, live subscription status,
per-relay connection state, per-tab last-updated timestamps,
and recent feed diagnostics log. Polls every 2s while visible.
Closes with Ctrl+Shift+D, Escape, or X button.

src/lib/feedDiagnostics.ts

@@ -32,6 +32,10 @@ function getLog(): DiagEntry[] {
   }
 }
 
+export function getRecentDiagEntries(count = 5): DiagEntry[] {
+  return getLog().slice(-count).reverse();
+}
+
 function saveLog(entries: DiagEntry[]) {
   localStorage.setItem(DIAG_KEY, JSON.stringify(entries.slice(-MAX_ENTRIES)));
 }

src/lib/nostr/core.ts

@@ -57,16 +57,22 @@ export function saveRelayUrls(urls: string[]) {
 }
 
 let ndk: NDK | null = null;
+let ndkCreatedAt: number | null = null;
 
 export function getNDK(): NDK {
   if (!ndk) {
     ndk = new NDK({
       explicitRelayUrls: getStoredRelayUrls(),
     });
+    ndkCreatedAt = Date.now();
   }
   return ndk;
 }
 
+export function getNDKUptimeMs(): number | null {
+  return ndkCreatedAt ? Date.now() - ndkCreatedAt : null;
+}
+
 /**
  * Destroy the current NDK instance and create a fresh one.
  * Preserves the signer (login state) but resets all relay connections.
@@ -87,6 +93,7 @@ export async function resetNDK(): Promise<void> {
   ndk = new NDK({
     explicitRelayUrls: getStoredRelayUrls(),
   });
+  ndkCreatedAt = Date.now();
 
   // Restore signer so user stays logged in
   if (oldSigner) {

src/lib/nostr/index.ts

@@ -1,4 +1,4 @@
-export { getNDK, connectToRelays, ensureConnected, resetNDK, getStoredRelayUrls, addRelay, removeRelay, fetchWithTimeout, withTimeout, FEED_TIMEOUT, THREAD_TIMEOUT, SINGLE_TIMEOUT } from "./core";
+export { getNDK, getNDKUptimeMs, connectToRelays, ensureConnected, resetNDK, getStoredRelayUrls, addRelay, removeRelay, fetchWithTimeout, withTimeout, FEED_TIMEOUT, THREAD_TIMEOUT, SINGLE_TIMEOUT } from "./core";
 export { fetchGlobalFeed, fetchFollowFeed, fetchUserNotes, fetchUserNotesNIP65, fetchNoteById, fetchReplies, publishNote, publishReply, publishRepost, publishQuote, fetchHashtagFeed, fetchThreadEvents, fetchAncestors } from "./notes";
 export { publishProfile, publishContactList, fetchProfile, fetchFollowSuggestions, fetchMentions, fetchNewFollowers } from "./social";
 export { publishArticle, fetchArticle, fetchAuthorArticles, fetchArticleFeed, searchArticles, fetchByAddr } from "./articles";