core: quiet transport reconnect spam for LAN-only / dead-server mode

SSE and RTC logged an error (and SSE flipped status) on every reconnect
attempt, so running without a reachable server — the legit LAN-only case —
flooded the log and spammed on_status(false). Now each transport reports a
drop once per outage streak and resets on reconnect; SSE no longer logs
per-send failures (implied by the connection-state line).

Verified: serverless agent↔peer LAN sync still works both directions, with the
agent log down from ~25 lines to 7 (one disconnect notice per transport, then
real activity).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

core/src/lib.rs

@@ -217,12 +217,21 @@ impl Transport for SseTransport {
             let min = Duration::from_millis(500);
             let max = Duration::from_secs(10);
             let mut backoff = min;
+            // Report a drop / log an error only once per outage streak — a dead
+            // or absent server (LAN-only mode) must not spam every retry.
+            let mut down_reported = false;
             while running.load(Ordering::SeqCst) {
                 match this.stream_once(&running, &sink, &status).await {
-                    Ok(()) => backoff = min, // clean EOF — reconnect promptly
+                    Ok(()) => {
+                        backoff = min; // clean EOF — reconnect promptly
+                        down_reported = false;
+                    }
                     Err(e) => {
-                        status(false);
-                        eprintln!("tethercore[{}]: {e}", this.name());
+                        if !down_reported {
+                            status(false);
+                            eprintln!("tethercore[{}]: {e}", this.name());
+                            down_reported = true;
+                        }
                     }
                 }
                 if running.load(Ordering::SeqCst) {
@@ -230,18 +239,16 @@ impl Transport for SseTransport {
                     backoff = (backoff * 2).min(max);
                 }
             }
-            status(false);
         });
     }
 
     fn publish(&self, rt: &Handle, msg: Message) {
         let http = self.http.clone();
         let cfg = self.cfg.clone();
-        let name = self.name();
         rt.spawn(async move {
-            if let Err(e) = post(&http, &cfg, &msg.text).await {
-                eprintln!("tethercore[{name}]: send failed: {e}");
-            }
+            // A failed send is already implied by the connection-state log;
+            // don't log per-send (every clipboard change would spam offline).
+            let _ = post(&http, &cfg, &msg.text).await;
         });
     }
 }

core/src/rtc.rs

@@ -419,10 +419,21 @@ impl Transport for RtcTransport {
             let min = Duration::from_millis(500);
             let max = Duration::from_secs(10);
             let mut backoff = min;
+            // Log a signaling error only once per outage streak (LAN-only / dead
+            // server must not spam).
+            let mut logged = false;
             while running.load(Ordering::SeqCst) {
                 match self.signal_stream(&running).await {
-                    Ok(()) => backoff = min,
-                    Err(e) => eprintln!("tethercore[rtc]: {e}"),
+                    Ok(()) => {
+                        backoff = min;
+                        logged = false;
+                    }
+                    Err(e) => {
+                        if !logged {
+                            eprintln!("tethercore[rtc]: {e}");
+                            logged = true;
+                        }
+                    }
                 }
                 if running.load(Ordering::SeqCst) {
                     tokio::time::sleep(backoff).await;