Fix: Cancel NIP-46 handshake on login modal cancellation

Implemented a mechanism to cancel the pending NIP-46 handshake when the user clicks 'Cancel' in the login modal.
- Added `pendingHandshakeCancel` callback to `NostrClient` to reject the handshake promise.
- Updated `LoginModalController` to invoke `disconnectRemoteSigner` on cancellation.
- Prevented `onLoginError` callback from triggering when the error code is `login-cancelled`.

Co-authored-by: PR0M3TH3AN <[email protected]>

js/nostr/client.js

@@ -1263,6 +1263,7 @@ export class NostrClient {
     this.unreachableRelays = new Set();
     this.isInitialized = false;
     this.nip46Client = null;
+    this.pendingHandshakeCancel = null;
     this.remoteSignerListeners = new Set();
     this.sessionActorListeners = new Set();
     const storedRemoteSigner = this.getStoredNip46Metadata();
@@ -1708,6 +1709,9 @@ export class NostrClient {
           return;
         }
         settled = true;
+        if (this.pendingHandshakeCancel === cancelHandshake) {
+          this.pendingHandshakeCancel = null;
+        }
         try {
           subscription?.unsub?.();
         } catch (error) {
@@ -1718,6 +1722,15 @@ export class NostrClient {
         }
       };
 
+      const cancelHandshake = () => {
+        cleanup();
+        const error = new Error("Remote signer connection cancelled.");
+        error.code = "login-cancelled";
+        reject(error);
+      };
+
+      this.pendingHandshakeCancel = cancelHandshake;
+
       const timeoutId = setTimeout(() => {
         cleanup();
         const error = new Error("Timed out waiting for the remote signer to acknowledge the connection.");
@@ -2438,6 +2451,16 @@ export class NostrClient {
    */
   async disconnectRemoteSigner({ keepStored = true } = {}) {
     this.pendingRemoteSignerRestore = null;
+
+    if (this.pendingHandshakeCancel) {
+      try {
+        this.pendingHandshakeCancel();
+      } catch (error) {
+        devLogger.warn("[nostr] Failed to cancel pending handshake:", error);
+      }
+      this.pendingHandshakeCancel = null;
+    }
+
     if (this.nip46Client) {
       try {
         await this.nip46Client.destroy();

js/ui/loginModalController.js

@@ -1487,6 +1487,7 @@ export default class LoginModalController {
             this.rejectPendingTask(this.createCancellationError(), {
               type: "add-profile",
             });
+            this.handleProviderDisconnect("nip46");
             cleanup();
           } else {
             finish(null, { keepMounted: false });
@@ -2392,6 +2393,13 @@ export default class LoginModalController {
           return;
         }
 
+        if (
+          rejectionError.code === "login-cancelled" ||
+          rejectionError.code === "user-cancelled"
+        ) {
+          return;
+        }
+
         await safeInvokeAsync(this.callbacks.onLoginError, {
           provider: entry.provider.source || entry.provider,
           error: rejectionError,