Use smaller test counts to reduce CI time while still detecting regression

Changed from (10, 100, 1000) to (10, 50, 200) values.

Since the bug scales exponentially, 200 values is sufficient to prove
the optimization works (without fix: 16s+, with fix: 150ms).

Benefits:
- Test runs in ~1-2s instead of 25-65s on CI with race detector
- Still catches performance regressions (10x+ speedup is obvious)
- More reliable on slow/variable CI runners
- Faster local development feedback

Verified on:
- Go 1.24.5 without race: 0.5ms, 11ms, 152ms ✓
- Go 1.24.5 with race: 3.2ms, 68ms, 916ms ✓
- Go 1.17.13 with race: 3.7ms, 71ms, 1.07s ✓

Author: Jecoms

decoder_test.go

@@ -1957,6 +1957,8 @@ func TestIssue71NestedPerformance(t *testing.T) {
 
 	// Adjust thresholds based on race detector
 	// Race detector adds 5-10x overhead, especially on older Go versions
+	// Using smaller counts (10, 50, 200) since we know the bug scales exponentially.
+	// Without the fix, even 200 values would take 10+ seconds.
 	var thresholds []struct {
 		numValues int
 		maxTime   time.Duration
@@ -1970,8 +1972,8 @@ func TestIssue71NestedPerformance(t *testing.T) {
 			maxTime   time.Duration
 		}{
 			{10, 50 * time.Millisecond},
-			{100, 500 * time.Millisecond},
-			{1000, 50 * time.Second}, // Extra lenient for slow CI runners
+			{50, 500 * time.Millisecond},  // Without fix: ~5s, with fix: ~50-100ms
+			{200, 5 * time.Second},        // Without fix: ~80s+, with fix: ~500ms-2s
 		}
 	} else {
 		// Strict thresholds for normal mode (local dev)
@@ -1981,8 +1983,8 @@ func TestIssue71NestedPerformance(t *testing.T) {
 			maxTime   time.Duration
 		}{
 			{10, 10 * time.Millisecond},
-			{100, 100 * time.Millisecond},
-			{1000, 10 * time.Second},
+			{50, 50 * time.Millisecond},   // Without fix: ~1s, with fix: ~5-10ms
+			{200, 500 * time.Millisecond}, // Without fix: ~16s, with fix: ~50-100ms
 		}
 	}