fix: detect system sleep and prevent false keepalive timeouts

When laptop wakes from sleep, the ping timer's elapsed time exceeds the normal
interval. This triggers immediate timeout checks on all clients that haven't
responded during the sleep period, causing false disconnections. Reset all
client pong timestamps after detecting wake events (>1.5x interval elapsed)
to give clients a fresh keepalive window.

Author: bjulian5

lua/claudecode/server/tcp.lua

@@ -247,6 +247,7 @@ end
 ---@return table? timer The timer handle, or nil if creation failed
 function M.start_ping_timer(server, interval)
   interval = interval or 30000 -- 30 seconds
+  local last_run = vim.loop.now()
 
   local timer = vim.loop.new_timer()
   if not timer then
@@ -255,19 +256,46 @@ function M.start_ping_timer(server, interval)
   end
 
   timer:start(interval, interval, function()
+    local now = vim.loop.now()
+    local elapsed = now - last_run
+
+    -- Detect potential system sleep: timer interval was significantly exceeded
+    -- Allow 50% grace period (e.g., 45s instead of 30s) to account for system load
+    local is_wake_from_sleep = elapsed > (interval * 1.5)
+
+    if is_wake_from_sleep then
+      -- After system sleep/wake, reset all client pong timestamps to prevent false timeouts
+      -- This gives clients a fresh keepalive window since the time jump isn't their fault
+      require("claudecode.logger").debug(
+        "server",
+        string.format("Detected potential wake from sleep (%.1fs elapsed), resetting client keepalive timers", elapsed / 1000)
+      )
+      for _, client in pairs(server.clients) do
+        if client.state == "connected" then
+          client.last_pong = now
+        end
+      end
+    end
+
     for _, client in pairs(server.clients) do
       if client.state == "connected" then
-        -- Check if client is alive
+        -- Check if client is alive (local connections, so use standard timeout)
         if client_manager.is_client_alive(client, interval * 2) then
           client_manager.send_ping(client, "ping")
         else
-          -- Client appears dead, close it
-          server.on_error("Client " .. client.id .. " appears dead, closing")
+          -- Client connection timed out - log at INFO level (this is expected behavior)
+          local time_since_pong = math.floor((now - client.last_pong) / 1000)
+          require("claudecode.logger").info(
+            "server",
+            string.format("Client %s keepalive timeout (%ds idle), closing connection", client.id, time_since_pong)
+          )
           client_manager.close_client(client, 1006, "Connection timeout")
           M._remove_client(server, client)
         end
       end
     end
+
+    last_run = now
   end)
 
   return timer