Group consecutive tool calls into a shared render block

[annzhang-db]

Summary

• Adds groupConsecutiveToolSegments to collapse runs of consecutive dynamic-tool segments into a single tool-group render block
• Replaces the inline partSegments.map render loop with renderBlocks.map, routing tool groups to a new MessageToolGroup component
• Extracts all tool rendering logic (MCP approval branch + regular tool branch) into a ToolPartRenderer component

Test plan

• Verify single tool calls render identically to before
• Verify consecutive tool calls are grouped into a shared wrapper
• Verify MCP approval flow still works (approve/deny buttons, state transitions)
• Verify OAuth inline errors still render correctly

This pull request and its description were written by Isaac.