memory-vector: LlmMemoryReviewer + SkillStore/SkillSaveTool/SkillDeleteTool

Phase 3 (Hermes-style self-improvement) and Phase 5.2 (LLM-driven review):

* :skills — SkillStore interface + DiskSkillStore (upsert/remove, file<->catalog sync)
* :skills — SkillParser.serialize for write-back path
* :standalone — SkillSaveTool/SkillDeleteTool + SkillToolsFactory
* :standalone — LlmMemoryReviewer: one-shot LiteLlm review via structured-output
  JSON prompt ({toSave:[...], toDelete:[...]}); reuses MemorySystem store
* :standalone — ReviewDecisionParser (lenient, handles json fences, missing
  arrays, malformed numbers)
* :standalone — ReviewPrompts (Russian system+user prompts, fact categories)
* :standalone/Main — wires LlmMemoryReviewer instead of KeywordMdReviewer when
  LLM is available, falls back to keyword for off/md-only mode
* :client — send(content, context) overload + SendPayload wrapper
* :proto — ExperimentalNativeApi opt-in for MessageContextTest (native targets)

Bug fixes:
* SkillTools.kt: error() shadowed kotlin.error(); renamed to Nothing
* ChatConversation: .map { when(...); error() } → .mapNotNull { when ... else -> null }
  (Kotlin type inference of LUB LiteMessage | Nothing failed across when-expr)

Tests: 284 total green (memory-vector: 17, standalone: 149).

Dropped: IRC-QUESTIONS.md (irc-server design rejected — user decision 2026-09-14).

client/src/main/kotlin/pw/binom/agentik/client/ConversationClient.kt

@@ -13,10 +13,12 @@ import io.ktor.http.HttpStatusCode
 import io.ktor.http.contentType
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flow
+import kotlinx.serialization.Serializable
 import pw.binom.agentik.proto.Content
 import pw.binom.agentik.proto.Conversation
 import pw.binom.agentik.proto.Event
 import pw.binom.agentik.proto.Message
+import pw.binom.agentik.proto.MessageContext
 import kotlin.time.Instant
 
 /**
@@ -58,10 +60,10 @@ internal class ConversationClient(
         snapshot = updated
     }
 
-    override suspend fun send(content: List<Content>) {
+    override suspend fun send(content: List<Content>, context: MessageContext?) {
         httpClient.post("$convUrl/messages") {
             contentType(ContentType.Application.Json)
-            setBody(content)
+            setBody(SendPayload(content, context))
         }
     }
 
@@ -92,3 +94,9 @@ internal class ConversationClient(
         // Agent.deleteConversation(id). См. [Conversation.close] KDoc.
     }
 }
+
+@Serializable
+private data class SendPayload(
+    val content: List<Content>,
+    val context: MessageContext? = null,
+)