chore(hygiene): ignore editor artifacts; prettier SignerScreen

- .gitignore now covers .directory, .opencode/, .impeccable/.
- SignerScreen.tsx reformatted (format:check was failing since 81b082f).
- Dead untracked stub src/signer/nip46_external.rs deleted from disk
  (superseded by nip46_client.rs, never declared in signer/mod.rs).

frontend/src/screens/SignerScreen.tsx

@@ -18,8 +18,15 @@ const EMPTY_STATUS: SignerStatus = {
 };
 
 export function SignerScreen() {
-  const { state, signerConnect, signerDisconnect, signerStatus, signerApprove, signerGrantsList, signerGrantRevoke } =
-    useApp();
+  const {
+    state,
+    signerConnect,
+    signerDisconnect,
+    signerStatus,
+    signerApprove,
+    signerGrantsList,
+    signerGrantRevoke,
+  } = useApp();
   const [status, setStatus] = useState<SignerStatus>(EMPTY_STATUS);
   const [grants, setGrants] = useState<SignerGrant[]>([]);
   const [uri, setUri] = useState('');
@@ -240,8 +247,7 @@ export function SignerScreen() {
             </header>
             <div className="card-body signer-pending">
               <p className="hint">
-                These requests run without asking. Revoke one to go back to approving it every
-                time.
+                These requests run without asking. Revoke one to go back to approving it every time.
               </p>
               {grants.map((grant) => (
                 <div key={`${grant.app_pubkey}:${grant.method}`} className="signer-pending-item">