standalone: add MCP client + tool-call loop

- Add mcp/McpConfig + McpRegistry wrapping io.modelcontextprotocol:kotlin-sdk-client 0.15.0
  - Supports stdio (uvx/npx/python) and streamable HTTP transports
  - Claude Desktop-compatible JSON config (AGENTIK_MCP_CONFIG)
  - server__tool name prefix to avoid collisions between servers
- Add agent/NamedTool (name + LiteTool pair) and tools: List<NamedTool> on ChatAgent/ChatConversation
- Implement tool-call loop in ChatConversation.runTurn:
  - delta.toolCalls -> emit ToolCall event -> persist audit -> execute tool
    -> emit ToolResult -> persist -> liteConv.addToolResult(callId, name, result)
  - separate tc-/tr- prefixes keep SQL PRIMARY KEY unique while toolCallId FK is preserved
- 8 McpConfig + 4 McpRegistry unit tests; +1 ChatAgentTest tool-loop test (44/44 total)
- e2e verified: real MCP fetch server (mcp-server-fetch) + litellm local/codding
  -> LLM calls fetch__fetch, MCP exec, result fed back, conversation continues

docs/STANDALONE.md: drop 'no tools / no MCP' from §8; replace 'Подключить тул (v2)' stub
with full in-agent + MCP recipe and tool-loop algorithm in §7

standalone/build.gradle.kts

@@ -57,6 +57,13 @@ kotlin {
             // Транспортные фасады
             implementation(libs.agui.server)
             implementation(libs.a2a.server)
+
+            // MCP (Model Context Protocol) клиент — подключение внешних/внутренних MCP-серверов
+            implementation(libs.mcp.sdk.client)
+            implementation(libs.ktor.client.core)
+            implementation(libs.ktor.client.cio)
+            implementation(libs.ktor.client.content.negotiation)
+            implementation(libs.ktor.serialization.kotlinx.json)
         }
 
         commonTest.dependencies {