ntm v1.21.0

Minor release: behavior-visible defaults changed (idle threshold, cursor-agent launcher) plus a batch of robustness fixes.

Features

Configurable idle threshold (#238): the [assign] config section gains an idle_threshold key; the default idle threshold is now 15m (was 120s). Long-thinking agents are no longer prematurely treated as idle.
Cursor-agent launcher (#233): cursor-agent is now a supported launcher with a sensible default command.
add-registration (#240): register an existing pane/agent with Agent Mail after the fact.
Agent lifecycle robot verbs: --robot-exit-cli / --robot-kill-agent for graceful agent CLI exit or kill without destroying the pane; ntm kill --pane / --robot-kill-pane for per-pane removal.
ntm rotate --force: bounded rotation of wedged agent CLIs.

Symlink-aware Agent Mail keys + real spawn identities (#239): project keys are canonicalized through symlinks and spawned agents register with their real identities.
Trust-prompt health detection (#230): trust/permission prompts are detected as needing attention instead of appearing healthy.
Silent send strand (#241): ntm send no longer reports "Sent" for prompts that never submit (e.g. a Claude Code pane parked on an open TUI menu).
Epic misdispatch (#242): the assign classifier now reads issue type — epics without a gate label are no longer auto-dispatched to worker panes as implementation work.
Pane-uptime reporting fixes since v1.20.0.
--robot-snapshot --since now derives deltas from the durable attention feed (survives process restarts); removed the dead process-local state tracker.
Loud INVALID_FLAG errors for empty lifecycle-verb values.
Serve/REST hardening: beads REST surface no longer perturbs tracker state; projectDir snapshotting fixed under lock.

curl -fsSL https://raw.githubusercontent.com/Dicklesworthstone/ntm/main/install.sh | bash