fix(nip46): give sign_event the human-approval timeout leash

Live pairing (Sep 23) proved the signer round-trip works: connect,
get_public_key and the first sign_event all succeeded against real
Amber. Subsequent signs failed because the client half used the 30s
ordinary-RPC leash for sign_event, while every sign waits on a human
approving the prompt on the signer's device. The log shows a valid
signature arriving ~61s after publication, after the waiter had been
removed: 'stale/duplicate response: no waiter ... dropped' — the user
watched failures while Amber was signing correctly.

sign_event now uses a 120s SIGN_TIMEOUT (same leash as the connect
handshake); get_public_key keeps the 30s retry-cadence timeout.

src/signer/nip46_client.rs

@@ -38,6 +38,13 @@ const REQUEST_TIMEOUT: Duration = Duration::from_secs(30);
 /// How long the connect handshake can involve a human approving the app on
 /// the signer's screen, so it gets a far longer leash than ordinary RPCs.
 const HANDSHAKE_TIMEOUT: Duration = Duration::from_secs(120);
+/// How long a `sign_event` may wait for the signer's answer. Like the
+/// handshake, every sign waits for a human to notice and approve the prompt
+/// on the signer's device, so it needs the same long leash rather than the
+/// 30s ordinary-RPC one: live pairing (Sep 23) showed a perfectly valid
+/// signature arriving after the 30s leash expired, discarded as
+/// "stale/duplicate response: no waiter" while the user watched failures.
+const SIGN_TIMEOUT: Duration = Duration::from_secs(120);
 /// How long a pairing QR (client-initiated `nostrconnect://`) stays live
 /// while a human opens their signer and scans it.
 const PAIRING_TIMEOUT: Duration = Duration::from_secs(300);
@@ -1153,12 +1160,16 @@ impl Nip46ClientSigner {
     /// return [`SigningError`] rather than falling back to any local key. The
     /// waiter is always removed from the pending map, even on timeout, so a
     /// late response to an abandoned request finds nothing to wake.
+    ///
+    /// Uses the human-approval leash ([`SIGN_TIMEOUT`]), not the 30s
+    /// ordinary-RPC one: every call here asks a human to approve on the
+    /// signer's device.
     async fn send_remote_request(
         &self,
         method: &str,
         params: Vec<String>,
     ) -> Result<String, SigningError> {
-        self.send_rpc(method, params, REQUEST_TIMEOUT, true).await
+        self.send_rpc(method, params, SIGN_TIMEOUT, true).await
     }
 
     /// Send an encrypted NIP-46 RPC and await its response.