mcp+tools: preserve JSON primitive types across the wire

McpLiteToolAdapter.parseArgsJson() used JsonPrimitive.content for every value
(always String), so MCP servers saw e.g. max_length:"500" and rejected
calls with '500' is not of type 'integer'. Replaced with kotlinx.serialization
booleanOrNull/intOrNull/longOrNull/doubleOrNull ladder that mirrors the
litert-openai parser.

ChatConversation.encodeArgsJson was also still calling encodeToolArgs
(stub from earlier pass). Inlined a small Any?.toJsonElement() helper
that preserves Boolean/Number/String/Map/List types when re-serializing
the LiteToolCall.arguments map into the argsJson string fed to
tool.invoke().

E2E re-verified: litellm local/codding + mcp-server-fetch now invokes
fetch__fetch({max_length:2000,url:...}) once, MCP gets a real
'Failed to fetch robots.txt' from the actual network sandbox instead
of rejecting the schema, LLM reports the real cause to the user.

standalone/src/jvmMain/kotlin/pw/binom/agentik/standalone/agent/ChatConversation.kt

@@ -359,7 +359,27 @@ class ChatConversation(
 
     private fun newId(prefix: String): String = "$prefix-${java.util.UUID.randomUUID()}"
 
-    private fun encodeArgsJson(arguments: Map<String, Any?>): String = encodeToolArgs(arguments)
+    private fun encodeArgsJson(arguments: Map<String, Any?>): String {
+        val el = kotlinx.serialization.json.JsonElement.serializer()
+        val obj = kotlinx.serialization.json.buildJsonObject {
+            arguments.forEach { (k, v) -> put(k, v.toJsonElement()) }
+        }
+        return kotlinx.serialization.json.Json.encodeToString(el, obj)
+    }
+
+    private fun Any?.toJsonElement(): kotlinx.serialization.json.JsonElement = when (this) {
+        null -> kotlinx.serialization.json.JsonNull
+        is Boolean -> kotlinx.serialization.json.JsonPrimitive(this)
+        is Number -> kotlinx.serialization.json.JsonPrimitive(this)
+        is String -> kotlinx.serialization.json.JsonPrimitive(this)
+        is Map<*, *> -> kotlinx.serialization.json.buildJsonObject {
+            this@toJsonElement.forEach { (k, v) ->
+                put(k.toString(), v.toJsonElement())
+            }
+        }
+        is List<*> -> kotlinx.serialization.json.JsonArray(this.map { it.toJsonElement() })
+        else -> kotlinx.serialization.json.JsonPrimitive(toString())
+    }
 
     companion object {
         private const val MAX_TOOL_LOOPS = 16

standalone/src/jvmMain/kotlin/pw/binom/agentik/standalone/mcp/McpRegistry.kt

@@ -22,7 +22,11 @@ import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.JsonObject
 import kotlinx.serialization.json.JsonPrimitive
+import kotlinx.serialization.json.booleanOrNull
 import kotlinx.serialization.json.buildJsonObject
+import kotlinx.serialization.json.doubleOrNull
+import kotlinx.serialization.json.intOrNull
+import kotlinx.serialization.json.longOrNull
 import kotlinx.serialization.json.put
 import pw.binom.agentik.standalone.agent.NamedTool
 import pw.binom.litert.LiteTool
@@ -234,10 +238,22 @@ internal class McpLiteToolAdapter(
         private fun JsonObject.toAnyMap(): Map<String, Any?> =
             entries.associate { (k, v) -> k to jsonElementToAny(v) }
 
+        /**
+         * Преобразует [JsonPrimitive] в типизированное значение (Boolean/Int/Long/Float/Double),
+         * и только в крайнем случае — в String. Без этого MCP-сервер получает все аргументы
+         * как строки и отвергает их по JSON-schema (например, `max_length:500` → `"500"` →
+         * «'500' is not of type 'integer'»).
+         */
         private fun jsonElementToAny(el: JsonElement): Any? = when (el) {
-            is JsonPrimitive -> el.content
+            is JsonPrimitive ->
+                el.booleanOrNull
+                    ?: el.intOrNull
+                    ?: el.longOrNull
+                    ?: el.doubleOrNull
+                    ?: if (el.isString) el.content else el.content
             is JsonArray -> el.map { jsonElementToAny(it) }
             is JsonObject -> el.toAnyMap()
+            else -> null
         }
     }
 }