Agents running outside tmux are silently uncoverable by the actuator: no statusline to read, no pane to keystroke, no alert (pm-llmmsgsrv-cc at 76.4% uncovered right now)

Found 2026-08-09 while auditing coverage across the venus OOM cascade. pm-llmmsgsrv-cc is running under a bare SSH bash session on pts/14 (PID 145512, parent chain sshd -> bash -> claude, elapsed 5h10m), NOT in tmux. tmux ls confirms no session of that name; has-session -t '=pm-llmmsgsrv-cc' returns 'can't find session'. Consequence: the venus actuator cannot cover it at all. Both halves of the loop go through tmux - read_pct() scrapes the statusline via sc.capture(), and send_keys() types into a pane. With no pane there is nothing to read and nothing to type into, so the agent can neither be measured nor actuated. Its last real sample is 2026-08-09T06:44:51 at ctx 76.4% with a persist nudge unanswered since 06:41:32, and analyze-agent-context.sh already reports two skip_compact_abrss_timeout escalation failures in 6h (05:30:56, 04:13:54). It is climbing toward native auto-compact with no coverage and nothing retrying. The defect is not that this one agent was launched oddly. It is that the actuator has NO detection for it. A tmux-less agent is silently indistinguishable from an agent that simply is not running, and both fall out of every trigger without alerting anyone. Right now 7 agents were sampled since 07:00 against 8 live tmux sessions, so the roster and the coverable set already disagree and nothing says so. Open question to settle before coding, do not assume the answer: at 06:41:32 send_keys logged 'tmux ok=True' for this agent. send_keys returns rc1==0 and rc2==0 from 'tmux send-keys -t <agent>', and tmux -t does PREFIX matching (documented trap in reference_analyze_agent_context_script). Either a session of that name still existed at 06:41 and exited by 06:45, or a nonexistent target returned success and the nudge went nowhere while being logged as delivered. The second case is the serious one - it would be a false-success on the send path, the same class as the 2026-08-01 paste-burst bug that send_keys' docstring was written for. Establish which by test (send-keys to a known-absent target, check rc) before changing anything. Fix direction: verify the target exists before claiming delivery, and emit an explicit uncoverable-agent event when a registered agent has no tmux session, so it alerts instead of silently dropping out.