- Renamed subagent completion flow from `submit_result` to `yield` across SDK tools, prompts, and docs.
- Updated executor/task handling to require and parse `yield` calls, replacing legacy submit-result extraction and state flags.
- Added `subagent-yield-reminder` and updated system prompts to require `yield` with `result.data` or `result.error`.
- Renamed hidden-tool and registration plumbing to `yield`, including discovery helpers and renderer/test surface.
- Exported `finalizeSubprocessOutput()` function and `SubmitResultItem` interface for subprocess output finalization with submit_result validation.
- Added automatic reminders (up to 3) when subagent stops without calling submit_result tool, aborting with exit code 1 after final reminder.
- Extracted subprocess output finalization logic into dedicated `finalizeSubprocessOutput()` function for improved testability and reusability.
- Added comprehensive test coverage for subagent warning injection, reminder behavior, and abort handling in executor module.
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