Add reflect.agent — a lateral-thinking subconscious agent that
observes the conversation and offers occasional reflections when the
conscious mind seems to be missing something.
Refactor memory_search.rs: extract generic agent_cycle_raw() from
the surface-specific code. PID tracking, timeout, spawn/reap logic
is now shared. Surface and reflect agents each have their own result
handler (handle_surface_result, handle_reflect_result) wired through
the common lifecycle.
