feat(viewer): time out the initial connect instead of hanging forever

endpoint.connect() has no built-in deadline, so an offline host, a stale
share code, or an unreachable relay left the viewer spinning silently with
no feedback — surfacing in the GUI as a permanent "Connecting…" with no
error. Wrap the connect in a 15s tokio::time::timeout (matching the host's
online() cap) and race it against ctrl-c, bailing with an actionable
message. The error reaches stderr, so the GUI's ChildProc stderr-tail
path renders it on the viewer screen.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/viewer/mod.rs

@@ -1,12 +1,19 @@
-use anyhow::{Context, Result};
+use anyhow::{Context, Result, bail};
 use iroh::Endpoint;
 use iroh::endpoint::presets;
 use iroh_tickets::endpoint::EndpointTicket;
+use std::time::Duration;
 use tokio::net::TcpListener;
 
 use crate::cli::ViewerOpts;
 use crate::common::{alpn::ALPN, output, signal};
 
+/// Cap on the initial QUIC connect. `endpoint.connect()` has no built-in
+/// deadline, so an offline host / stale code / unreachable relay otherwise
+/// hangs forever with no feedback (the silent "connecting…" failure mode).
+/// Matches the host's 15s `online()` cap.
+const CONNECT_TIMEOUT: Duration = Duration::from_secs(15);
+
 pub async fn run(ticket: EndpointTicket, opts: ViewerOpts) -> Result<()> {
     let cancel = signal::install_ctrl_c();
 
@@ -17,7 +24,32 @@ pub async fn run(ticket: EndpointTicket, opts: ViewerOpts) -> Result<()> {
 
     let addr = ticket.endpoint_addr().clone();
     tracing::info!(remote = %addr.id, "connecting to host");
-    let conn = endpoint.connect(addr, ALPN).await?;
+
+    // Bound the connect attempt and let ctrl-c abort it, so the viewer fails
+    // loud (and the GUI surfaces the error) instead of spinning indefinitely.
+    let conn = tokio::select! {
+        _ = cancel.cancelled() => {
+            tracing::info!("ctrl-c received before the connection was established");
+            endpoint.close().await;
+            return Ok(());
+        }
+        result = tokio::time::timeout(CONNECT_TIMEOUT, endpoint.connect(addr, ALPN)) => match result {
+            Ok(Ok(conn)) => conn,
+            Ok(Err(e)) => {
+                endpoint.close().await;
+                bail!("failed to connect to the host: {e:#}");
+            }
+            Err(_) => {
+                endpoint.close().await;
+                bail!(
+                    "couldn't reach the host within {}s — it may be offline, the share \
+                     code may be stale, or the relay may be unreachable. Check that the \
+                     host is running, then re-copy the code and try again.",
+                    CONNECT_TIMEOUT.as_secs()
+                );
+            }
+        },
+    };
     let (quic_send, quic_recv) = conn.open_bi().await?;
 
     let listener = TcpListener::bind(("127.0.0.1", opts.port)).await?;