New handling for requests whose old tool results were cut

What

A tool call is a single action Claude takes, such as reading a file, and its output is the tool result. Claude Code now recognises requests where old tool results have been replaced with placeholders.

• Attachment: a tool_results_cut attachment type is handled, and cut_request_id is accepted as a request id next to suppressed_request_id.
• Teleport relay: when a request replaces old tool results with placeholders, the relay falls back to the standard path, logs the reason tool_results_cut, and reports whether placeholders are being sent. The relay's tools-used header handling also changed, so its MCP flag no longer depends on a second check.
• Reason labels: tool_results_cut was added to a list of reasons, and a new vm_unavailable case sits next to cloud_unavailable and network_off.

Why

These changes point to a way of trimming old tool output from a conversation. Where history has been rewritten like this, the relay uses the normal path instead of passing it on.