Tool group count fix for chat history

This patch release fixes an issue where tool group counts showed inflated numbers when loading chat history.

Bug fixes

• Tool group count showing inflated numbers #1483  - Fixed tool group count displaying inflated numbers when loading chat history. The server accumulates all tool calls from a turn into each assistant message, causing duplicate tool-call parts when converting messages for the UI. Added deduplication in the message converter so each tool call appears only once. Also fixed buildAssistantContentParts silently dropping tool calls when assistant content is a string. (Author: @adaam2 )