Forward the previously-dropped `locations` and `meta` fields from ACP
SDK ToolCall/ToolCallUpdate events through to the frontend. The meta
field carries `claudeCode.parentToolUseId` which enables precise
parent-child matching for concurrent Agent tool calls during streaming.
- Forward locations/meta in Rust AcpEvent types and connection handlers
- Use parentToolUseId for exact agent→child mapping, with position-based
fallback for agents that don't provide it (Codex, OpenCode)
- Replace `any` types with proper ToolCallMeta / unknown types
- Add runtime guards for meta field parsing (defensive against
unexpected shapes from different agents)
- Cache inferLiveToolName results per tool_call_id to avoid redundant
computation across Phase 1 and Phase 2
- Lazy-construct agentStats only when children exist
834340e536