Merge branch 'structured-output-subagent-seam' into worktree-dynamic-workflows

# Conflicts:
#	examples/acp-agent/tests/snapshots/cancel/session.jsonl
#	examples/acp-agent/tests/snapshots/error-finish/session.jsonl
#	examples/acp-agent/tests/snapshots/fs-edit/session.jsonl
#	examples/acp-agent/tests/snapshots/fs-policy-reject/session.jsonl
#	examples/acp-agent/tests/snapshots/fs-read-window/session.jsonl
#	examples/acp-agent/tests/snapshots/fs-read/session.jsonl
#	examples/acp-agent/tests/snapshots/fs-terminal-card/session.jsonl
#	examples/acp-agent/tests/snapshots/fs-write-overwrite/session.jsonl
#	examples/acp-agent/tests/snapshots/fs-write/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-cc-posttool-block/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-cc-posttool-context/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-cc-pretool-ask/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-cc-pretool-deny/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-cc-promptsubmit-context/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-cc-stop-continue/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-codex-posttool-block/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-codex-posttool-context/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-codex-pretool-block/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-codex-promptsubmit-context/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-codex-stop-continue/session.jsonl
#	examples/acp-agent/tests/snapshots/multi-turn/session.jsonl
#	examples/acp-agent/tests/snapshots/subagent-fork/session.1.jsonl
#	examples/acp-agent/tests/snapshots/subagent-fork/session.jsonl
#	examples/acp-agent/tests/snapshots/subagent-mixed/session.1.jsonl
#	examples/acp-agent/tests/snapshots/subagent-mixed/session.2.jsonl
#	examples/acp-agent/tests/snapshots/subagent-mixed/session.jsonl
#	examples/acp-agent/tests/snapshots/subagent-multi/session.1.jsonl
#	examples/acp-agent/tests/snapshots/subagent-multi/session.2.jsonl
#	examples/acp-agent/tests/snapshots/subagent-multi/session.jsonl
#	examples/acp-agent/tests/snapshots/subagent-spawn/session.1.jsonl
#	examples/acp-agent/tests/snapshots/subagent-spawn/session.jsonl
#	examples/acp-agent/tests/snapshots/todo-plan/session.jsonl
#	examples/acp-agent/tests/snapshots/tool-call-turn/session.jsonl
#	examples/acp-agent/tests/snapshots/workspace-edit/session.jsonl

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