sched: fix runner leak during reloading unload (#10819)

When the same model is being reloaded rapidly with client connections
being canceled before the model finishes loading, the queued unload
event could cause a leak of runners by deleting a different runner from
the loaded list.

server/sched.go

@@ -387,6 +387,17 @@ func (s *Scheduler) processCompleted(ctx context.Context) {
 				s.loadedMu.Unlock()
 				runner.refMu.Unlock()
 				slog.Debug("duplicate expired event, ignoring", "runner", runner)
+			} else if runner.pid != runnerToUnload.pid {
+				// If the pids do not match, we likely had multiple load
+				// failures for the same model in quick succession due to
+				// request context canceled and are draining the queue of
+				// events. Ensure the orphaned runner is properly shut down, but
+				// do not delete the mismatched loaded runner, or wait for VRAM
+				// convergence.
+				slog.Debug("orphaned runner shutting down", "orphan", runner, "loaded", runnerToUnload)
+				runner.unload()
+				s.loadedMu.Unlock()
+				runner.refMu.Unlock()
 			} else {
 				slog.Debug("starting background wait for VRAM recovery", "runner", runner)
 				finished := runner.waitForVRAMRecovery()