MCP tool results now carry resource_links separately from _meta

Tool result messages now include a resource_links field that collects the raw resource_link content blocks returned by an MCP tool (up to 50 links or 64 KiB), as a sibling to _meta on tool_use_result.mcpMeta. This lets a host render referenced files directly instead of parsing the [Resource link: NAME] URI text line; it is absent for subagent tool results. Both live MCP tool calls and MCP task-based tool calls now capture and pass through resourceLinks/resource_links, including in the background-task terminal summary.