Print mode prints each turn's result as it ends and explains long waits

What

Print mode is the non-interactive way of running Claude Code with claude -p, where it answers and exits instead of opening a chat screen. Several of its outputs change:

• Text results can now be printed as each turn ends, not only when Claude Code exits. Empty successful results are skipped, and several results are separated by blank lines. This is controlled by the gate tengu_jazzy_puddle; nothing has been read about its state.
• When input is closed and Claude Code keeps waiting on background tasks or a scheduled wakeup, it now prints a one-time notice saying what it is waiting for (Waiting for background work to finish). It goes to stderr (the error output) or the debug log.
• The content_block_stop, message_delta and message_stop events in the live SDK stream (the event feed a program reads when driving Claude Code from code) are now built with extra context added into them.

Why

Headless runs that looked stuck now say why they are waiting. Scripts that run several turns may now see intermediate results printed, and programs that read stream events may see extra fields on those three events.