refactor: add relayHints seam to ICacheProvider (Phase 2 prep)

The shared user/event finder filter functions read LocalCache.relayHints
statically to discover which relays likely hold a user's metadata or a missing
event. To let those functions move to commonMain, expose the HintIndexer
(a quartz type) on ICacheProvider. Implement it on Android LocalCache
(override the existing field), add one to DesktopLocalCache, and satisfy the
four commonTest stub caches.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

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

@@ -479,7 +479,7 @@ object LocalCache : ILocalCache, ICacheProvider, Dao {
     @Volatile
     var lnurlEndpointResolver: LnurlEndpointResolver? = null
 
-    val relayHints = HintIndexer()
+    override val relayHints = HintIndexer()
 
     /**
      * Cashu mint URL directory, populated passively as

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/cache/ICacheProvider.kt

@@ -27,6 +27,7 @@ import com.vitorpamplona.amethyst.commons.model.User
 import com.vitorpamplona.quartz.nip01Core.core.Address
 import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.hints.HintIndexer
 
 /**
  * Cache provider interface for accessing cached Notes, Users, and Channels.
@@ -41,6 +42,13 @@ import com.vitorpamplona.quartz.nip01Core.core.HexKey
  * - Platform-agnostic model layer
  */
 interface ICacheProvider {
+    /**
+     * NIP-hints index (event/address/pubkey → relay) accumulated from consumed
+     * events. Used by the shared user/event finder assemblers to discover which
+     * relays are likely to hold a given user's metadata or a missing event.
+     */
+    val relayHints: HintIndexer
+
     /**
      * Gets a channel by Note reference.
      * Used for resolving relay hints for channel messages.

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/model/ThreadAssemblerTest.kt

@@ -25,6 +25,7 @@ import com.vitorpamplona.amethyst.commons.model.cache.ICacheProvider
 import com.vitorpamplona.quartz.nip01Core.core.Address
 import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.hints.HintIndexer
 import com.vitorpamplona.quartz.nip10Notes.TextNoteEvent
 import com.vitorpamplona.quartz.nip22Comments.CommentEvent
 import com.vitorpamplona.quartz.nip25Reactions.ReactionEvent
@@ -173,6 +174,8 @@ class ThreadAssemblerTest {
     ) : ICacheProvider {
         override fun getAnyChannel(note: Note): Channel? = null
 
+        override val relayHints = HintIndexer()
+
         override fun getUserIfExists(pubkey: HexKey): User? = null
 
         override fun countUsers(predicate: (String, User) -> Boolean): Int = 0

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/model/concord/ConcordChannelListLeaveTest.kt

@@ -33,6 +33,7 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.hexToByteArray
 import com.vitorpamplona.quartz.nip01Core.crypto.KeyPair
+import com.vitorpamplona.quartz.nip01Core.hints.HintIndexer
 import com.vitorpamplona.quartz.nip01Core.signers.NostrSignerInternal
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -82,6 +83,8 @@ class ConcordChannelListLeaveTest {
     private class StubCache : ICacheProvider {
         override fun getAnyChannel(note: Note): Channel? = null
 
+        override val relayHints = HintIndexer()
+
         override fun getUserIfExists(pubkey: HexKey): User? = null
 
         override fun countUsers(predicate: (String, User) -> Boolean): Int = 0

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/model/concord/ConcordListLateArrivalTest.kt

@@ -33,6 +33,7 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.hexToByteArray
 import com.vitorpamplona.quartz.nip01Core.crypto.KeyPair
+import com.vitorpamplona.quartz.nip01Core.hints.HintIndexer
 import com.vitorpamplona.quartz.nip01Core.signers.NostrSignerInternal
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -80,6 +81,8 @@ class ConcordListLateArrivalTest {
 
         override fun getAnyChannel(note: Note): Channel? = null
 
+        override val relayHints = HintIndexer()
+
         override fun getUserIfExists(pubkey: HexKey): User? = null
 
         override fun countUsers(predicate: (String, User) -> Boolean): Int = 0

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/ui/note/ReplyContextTest.kt

@@ -29,6 +29,7 @@ import com.vitorpamplona.amethyst.commons.model.cache.ICacheProvider
 import com.vitorpamplona.quartz.nip01Core.core.Address
 import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.hints.HintIndexer
 import com.vitorpamplona.quartz.nip10Notes.TextNoteEvent
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -113,6 +114,8 @@ class ReplyContextTest {
     ) : ICacheProvider {
         override fun getAnyChannel(note: Note): Channel? = null
 
+        override val relayHints = HintIndexer()
+
         override fun getUserIfExists(pubkey: HexKey): User? = users[pubkey]
 
         override fun countUsers(predicate: (String, User) -> Boolean): Int = 0

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/cache/DesktopLocalCache.kt

@@ -35,6 +35,7 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.crypto.checkSignature
 import com.vitorpamplona.quartz.nip01Core.crypto.verify
+import com.vitorpamplona.quartz.nip01Core.hints.HintIndexer
 import com.vitorpamplona.quartz.nip01Core.metadata.MetadataEvent
 import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
 import com.vitorpamplona.quartz.nip01Core.tags.aTag.taggedAddresses
@@ -90,6 +91,9 @@ class DesktopLocalCache : ICacheProvider {
     val addressableNotes = LargeSoftCache<String, AddressableNote>()
     private val deletedEvents = ConcurrentHashMap.newKeySet<HexKey>()
 
+    /** NIP-hints index accumulated from consumed events (event/address/pubkey → relay). */
+    override val relayHints = HintIndexer()
+
     val eventStream = DesktopCacheEventStream()
 
     /** Local relay store for persisting events to SQLite. Set from Main.kt on account login. */