fix: reject kind:1059 gift wraps with empty content before caching

A gift wrap with an empty content string carries no NIP-44 ciphertext,
so it can never be unwrapped. Filtering it at LocalCache's ingestion
choke point (justConsumeInnerInner) rejects it before the Schnorr
signature check and before it takes a permanent cache slot, and keeps
GiftWrapEventHandler from retrying a doomed unwrap on every batch.

Locally stripped wraps (copyNoContent, used to drop the ciphertext
after a successful unwrap) are assigned directly to note.event and
never pass through justConsume, so they are unaffected.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011A6iSrJJHUoz686eDnCQMV

amethyst/src/main/java/com/vitorpamplona/amethyst/model/LocalCache.kt

@@ -3847,7 +3847,15 @@ object LocalCache : ILocalCache, ICacheProvider {
                 }
 
                 is GiftWrapEvent -> {
-                    consumeRegularEvent(event, relay, wasVerified)
+                    // A wrap with an empty content carries no NIP-44 ciphertext and can
+                    // never be unwrapped — reject it before paying for a signature check
+                    // and a cache slot. Locally stripped copies (copyNoContent) are
+                    // assigned straight to note.event and never pass through here.
+                    if (event.content.isEmpty()) {
+                        false
+                    } else {
+                        consumeRegularEvent(event, relay, wasVerified)
+                    }
                 }
 
                 is GroupEvent -> {