feat(signer): surface an actionable notice when the signer goes unresponsive

A raw window.nostr probe in the user's browser (getPublicKey → nip04.encrypt
→ nip04.decrypt, bypassing ALL of bitvid) HUNG forever, with the extension's
own console showing `ObjectMultiplex - orphaned data for "background-liveness"`
+ `malformed chunk` + listener-leak warnings. That is the NIP-07 extension's
content-script ↔ background-service-worker channel being dead (classic MV3
worker death) — an extension/environment failure, not a bitvid bug. No client
change can force an unresponsive signer to answer; the fix is to reload/unlock
the extension.

What bitvid CAN do is stop failing silently. Add js/utils/signerHealthNotice.js:
after a few consecutive list-decrypt timeouts while the signer reports itself
present, emit ONE rate-limited, actionable user notice ("your signer isn't
responding to decryption — unlock/reload the extension and refresh") instead of
the silent 15-minute retry loop. Reset on any decrypt success so a transient
blip doesn't warn. Wired into blocks, hashtags, and subscriptions.

Also documents the definitive root-cause + all resilience increments in
KNOWN_BUGS #0. Test: tests/signer-health-notice.test.mjs (threshold, rate-limit,
success-reset). Full unit suite green.

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

js/subscriptions.js

@@ -27,6 +27,10 @@ import { getApplication } from "./applicationContext.js";
 import { VideoListView } from "./ui/views/VideoListView.js";
 import { ALLOW_NSFW_CONTENT } from "./config.js";
 import { devLogger, userLogger } from "./utils/logger.js";
+import {
+  noteSignerDecryptTimeout,
+  noteSignerDecryptSuccess,
+} from "./utils/signerHealthNotice.js";
 import moderationService from "./services/moderationService.js";
 import nostrService from "./services/nostrService.js";
 import { profileCache } from "./state/profileCache.js";
@@ -761,7 +765,11 @@ class SubscriptionsManager {
         this.uiReady = true;
         if (isTransientDecryptError(decryptResult.error)) {
           // Channel/timeout failures recover shortly — retry instead of
-          // abandoning the subscription list until a page refresh.
+          // abandoning the subscription list until a page refresh. A present
+          // signer that won't answer feeds the shared unresponsive notice.
+          if (decryptResult.error?.code === "subscriptions-decrypt-timeout") {
+            noteSignerDecryptTimeout("subscriptions");
+          }
           this.scheduleDecryptRetry(normalizedUserPubkey, decryptResult.error, {
             allowPermissionPrompt,
             signerReadinessGate,
@@ -837,6 +845,7 @@ class SubscriptionsManager {
       }
 
       this.decryptRetryAttempt = 0;
+      noteSignerDecryptSuccess();
 
       const decryptedStr = decryptResult.plaintext;
       const normalized = parseSubscriptionPlaintext(decryptedStr);