fix(remoteingress-core): improve tunnel liveness handling and enable TCP keepalive for accepted client sockets

rust/crates/remoteingress-protocol/src/lib.rs

@@ -32,6 +32,15 @@ pub fn encode_window_update(stream_id: u32, frame_type: u8, increment: u32) -> V
     encode_frame(stream_id, frame_type, &increment.to_be_bytes())
 }
 
+/// Compute the target per-stream window size based on the number of active streams.
+/// Total memory budget is ~32MB shared across all streams. As more streams are active,
+/// each gets a smaller window. This adapts to current demand — few streams get high
+/// throughput, many streams save memory and reduce control frame pressure.
+pub fn compute_window_for_stream_count(active: u32) -> u32 {
+    let per_stream = (32 * 1024 * 1024u64) / (active.max(1) as u64);
+    per_stream.clamp(64 * 1024, INITIAL_STREAM_WINDOW as u64) as u32
+}
+
 /// Decode a WINDOW_UPDATE payload into a byte increment. Returns None if payload is malformed.
 pub fn decode_window_update(payload: &[u8]) -> Option<u32> {
     if payload.len() != 4 {