Add structured daemon waiting input

[TZZheng]

Summary

Adds a structured waiting-input path for daemon CLI backends so a daemon can explicitly request parent/human input instead of burying a clarification question in final prose.

What changed

• Adds daemon_common.ask_human(question, choices?, default?, reason?) for MCP-capable daemon backends.
• Records the request via a dedicated input-request artifact and transitions the daemon into a runtime-owned waiting_input state.
• Surfaces waiting-input state through daemon list/check output and notification/event metadata without consuming the existing once-only terminal notification semantics for done/failed/cancelled/timeout.
• Keeps full request details in daemon state/check artifacts while bounding list previews to avoid context bloat.
• Routes corrupt or invalid direct request artifacts to failed so a daemon cannot remain stuck as running if it bypasses MCP validation.
• Documents the contract and Claude Code print-mode behavior.

Why

Claude Code print mode (claude --print) is not an interactive terminal: stdin is not a TTY, and clarification questions emitted as prose are only final/stdout text. A daemon needs a structured signal for "I need input" so the parent can receive a notification and decide whether to answer, ask the human, cancel, or rerun.

Non-goals / deferred

• This does not pretend claude --print can block on stdin.
• Automatic answer-to-resume state reconciliation is explicitly deferred; resumable CLI backends can receive a follow-up, but clearing/reconciling paused state after an answer remains follow-up lifecycle work.
• This does not broaden GitHub, shell, or live-runtime permissions for daemon tasks.

Validation

• git diff --check canonical/main...HEAD
• PYTHONPATH=src python -m py_compile src/tools/daemon/__init__.py src/tools/daemon/run_dir.py src/lingtai/mcp_servers/daemon_common/server.py
• PYTHONPATH=src python -m pytest -q tests/test_daemon_waiting_input.py tests/test_daemon_run_dir.py tests/test_daemon_terminal_state_gate.py tests/test_daemon_check.py — 111 passed
• PYTHONPATH=src python -m pytest -q tests/test_daemon*.py — 479 passed

Review

• Codex implementation and fix daemons completed local validation.
• Independent Claude Code review initially requested changes for corrupt direct request artifacts; the follow-up commit fixed that blocker.
• Claude Code re-review verdict: approve with nits. Remaining nits are non-blocking: a benign duplicate failure event on one backend path, choice-preview cap lacking an explicit truncation marker, and an existing permissive run_id: None behavior.