Harden runtime recovery against silent stuck turns

[dmoliveira]

Summary

• harden runtime recovery so delegated task aborts, long tool-only turns, and short continue-intent replies recover with visible parent progress instead of going silent
• make child idle recovery evidence-based and extend stale-session repair tooling to reconcile legacy delegated silent-parent findings in the runtime DB
• add regression coverage for recovery hooks and validate the repaired session database now passes /session doctor

Validation

• node --test plugin/gateway-core/test/session-recovery-hook.test.mjs plugin/gateway-core/test/long-turn-watchdog-hook.test.mjs plugin/gateway-core/test/todo-continuation-enforcer-hook.test.mjs plugin/gateway-core/test/subagent-lifecycle-supervisor-hook.test.mjs
• python3 -m py_compile scripts/session_command.py
• python3 scripts/session_command.py repair-stale --db-path "$HOME/.local/share/opencode/opencode.db" --stale-seconds 300 --apply --json
• python3 scripts/session_command.py doctor --json