Streaming output can be held longer when nobody is watching

What

When Claude Code runs under an SDK or remote host, it sends its output as a stream of events (stream-json). An environment variable is a setting passed to a program when it starts. This release adds several:

• set_has_subscribers is a new control request a host can send to say whether anyone is watching the stream-json output.
• CLAUDE_CODE_STREAM_EVENT_NO_SUBSCRIBER_HOLD_MS is passed as noSubscriberHoldMs next to the existing CLAUDE_CODE_STREAM_EVENT_HOLD_MS. With the hold variable set and no subscribers, each hold lasts the no-subscriber time if that is longer.
• CLAUDE_CODE_DISABLE_RESUME_LOAD_GOODBYE_SKIP narrows a resume behaviour. The worker's goodbye is now skipped during resume load only when this variable is unset and skipsGoodbyeDuringResumeLoad() is true. Before, the skip depended only on the resume-load check.
• CLAUDE_CODE_TRANSCRIPT_TAIL_LOAD and CLAUDE_CODE_THREAD_CPU_ONE_IN are new names in this build. Only the list entries were seen, not the code that reads them. From their names they appear to cover loading only the end of a transcript and thread CPU sampling.
• CLAUDE_CODE_DISABLE_TRANSCRIPT_READ_AHEAD was already present and now also appears in these lists.

CLAUDE_CODE_TRANSCRIPT_TAIL_LOAD and CLAUDE_CODE_STREAM_EVENT_NO_SUBSCRIBER_HOLD_MS sit in the environment allowlists next to CLAUDE_CODE_TRANSCRIPT_SLIM_TOOL_RESULTS and CLAUDE_CODE_STREAM_EVENT_HOLD_MS. CLAUDE_CODE_THREAD_CPU_ONE_IN is added to a separate check.

Why

SDK hosts can let Claude Code batch streaming output more when nobody is watching it. Remote or worker sessions that resume skip the goodbye in fewer cases, and CLAUDE_CODE_DISABLE_RESUME_LOAD_GOODBYE_SKIP turns that skip off.