Remove plans/ directory (P0/P1/P2 work complete)

vfs/locks/sharding.go

@@ -24,5 +24,8 @@ func GetKeyLock(keyLocks []sync.Map, key string) *sync.RWMutex {
 	shard := &keyLocks[shardIndex]
 
 	keyLock, _ := shard.LoadOrStore(key, &sync.RWMutex{})
-	return keyLock.(*sync.RWMutex)
+	if rl, ok := keyLock.(*sync.RWMutex); ok {
+		return rl
+	}
+	panic("corrupted lock shard: expected *sync.RWMutex")
 }