Fix GuestDataPool lease leak on non-GPU compute dispatch paths (#759)

ObserveComputeDispatch only returned evaluation's pooled arrays when
evaluationHandledByCpu was set. Dispatches rejected before submission
(empty resource tables, oversized workgroup, compile failure) or a
compute submit that got dropped instead of enqueued (workSequence == 0)
never handed those buffers to a consumer that would return them,
leaking one lease per occurrence and growing GuestDataPool.Shared
without bound over a long session.

Adds GuestDataPool.DiagnosticStats() (outstanding lease count, idle
cached bytes) surfaced in the periodic [LOADER][PERF] line, to catch
this class of regression going forward.

Verified on Ghost of Yotei and Demon's Souls: pool_leases grew
unbounded before the fix (525 in 5 min on Demon's Souls, 1114 in 180s
on Yotei) and stays flat/bounded after (0-6 and 2-18 respectively),
with no behavioral regression observed.

src/SharpEmu.Libs/VideoOut/VideoOutExports.cs

@@ -1300,10 +1300,12 @@ public static class VideoOutExports
         var submitted = Interlocked.Exchange(ref _submittedFrameCount, 0);
         var presentedCount = Interlocked.Exchange(ref _presentedFrameCount, 0);
         var (draws, drawMs, pipelines, spirvCompiles) = GuestGpu.Current.ReadAndResetPerfCounters();
+        var (poolLeases, poolCachedBytes) = SharpEmu.Libs.Gpu.GuestDataPool.DiagnosticStats();
         Console.Error.WriteLine(
             $"[LOADER][PERF] videoout submitted_fps={submitted / elapsedSeconds:F1} " +
             $"presented_fps={presentedCount / elapsedSeconds:F1} " +
-            $"draws={draws} draw_ms={drawMs:F0} pipelines={pipelines} spirv={spirvCompiles}");
+            $"draws={draws} draw_ms={drawMs:F0} pipelines={pipelines} spirv={spirvCompiles} " +
+            $"pool_leases={poolLeases} pool_cached_mb={poolCachedBytes / 1024.0 / 1024.0:F1}");
     }
 
     private static readonly bool _flipPacingDisabled = string.Equals(