* Move port scanning from shell to app-side with batching
Replace per-shell `ps -axo + lsof` scanning with a centralized
PortScanner singleton in the app. Each shell now sends lightweight
`report_tty` (once per session) and `ports_kick` (on preexec/precmd)
socket messages. The app coalesces kicks across all panels and runs a
single `ps -t <ttys> + lsof -p <pids>` covering every active panel.
Also fixes a macOS 26 Tahoe regression where `getsockopt(LOCAL_PEERPID)`
returns ENOTCONN on accepted sockets when the peer disconnects before
the handler thread starts. This was silently breaking ALL socket
commands sent via ncat --send-only. The fix captures the peer PID in
the accept loop immediately after accept(), and falls back to
LOCAL_PEERCRED (uid check) when the PID lookup fails.
* Fix PR review feedback: burst timing and auth comment clarity
- P2: burstDelays were accumulating (0.5+1.5+3+... = ~22.5s) instead of
firing at absolute offsets from burst start. Now uses burstStart anchor
so scans fire at 0.5s, 1.5s, 3s, 5s, 7.5s, 10s as intended.
- P1: Clarify LOCAL_PEERCRED fallback rationale — same security boundary
as socket file permissions (0600), does not widen attack surface.
Long-lived connections still get full descendant check via LOCAL_PEERPID.
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