fix(cache): enforce entry cap below ten in memory cache

The count-based eviction removed a tenth of the cap. For a cap under ten, that was zero entries, so the cache grew without limit. The cache now evicts at least one entry when it is full.

cache/memory/small_cap_test.go

@@ -0,0 +1,23 @@
+package libpack_cache_memory
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// Pins theorems/Theorems/MemCacheCap.lean: every cap >= 1 bounds the entry count.
+func TestSet_SmallEntryCapIsEnforced(t *testing.T) {
+	for _, maxEntries := range []int64{1, 2, 5, 9, 10, 25} {
+		t.Run(fmt.Sprintf("cap_%d", maxEntries), func(t *testing.T) {
+			c := NewWithSize(time.Minute, DefaultMaxMemorySize, maxEntries)
+			defer c.Shutdown()
+			for i := 0; i < 100; i++ {
+				c.Set(fmt.Sprintf("k%d", i), []byte("v"), time.Minute)
+				assert.LessOrEqual(t, c.CountQueries(), maxEntries)
+			}
+		})
+	}
+}