pub fn is_working(last_activity_at: Option<f64>, now_unix: f64) -> boolExpand description
#428: classify an agent’s activity from its heartbeat marker mtime
(see AgentInfo::last_activity_at). Working iff the marker was
touched within HEARTBEAT_FRESH_SECS of now_unix (strict <); a
missing (None) or stale marker is Idle. Pure + total so the 15s
boundary is unit-testable without touching the filesystem. #429 (C2b)
calls this to pick the working/idle glyph; Stopped/Unknown agents are
classified by state before this is ever consulted.