secondary-sdr: fix ADS-B on real hardware (tested on radio-box)

First hardware test of node-26#9/#10 found three blockers:
- antirez/dump1090 has no --write-json, so ADS-B mode exited on start.
  Swapped to wiedehopf/readsb; map alt_baro/gs (old names as fallback).
- op25 is not always on RTL-SDR index 0 (radio-box: op25 on 1, 0 free).
  start() now tries each index and keeps the first decoder that stays up.
  AIS-catcher index flag fixed to -d:N ("-d N" selects by serial).
- status() reported "running" for a decoder that died on startup: the
  zombie still answered killpg(pgid, 0). Liveness now via Popen.poll().

install.sh blacklists dvb_usb_rtl28xxu, which claimed the second dongle.

Verified on radio-box: 831 msgs/min, 6 aircraft (3 with position) on a
9cm whip; op25 unaffected. AIS still untested.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

install.sh

@@ -181,6 +181,13 @@ else
   warn "no RTL-SDR dongle detected on USB — plug one in before expecting audio"
 fi
 
+# The kernel's DVB-TV driver auto-binds RTL2838 dongles. op25 detaches it from
+# the one it opens, but any other dongle stays claimed and the secondary-sdr
+# decoder fails with "usb_claim_interface error -6" (node-26#9).
+echo "blacklist dvb_usb_rtl28xxu" > /etc/modprobe.d/blacklist-rtl-sdr.conf
+modprobe -r rtl2832_sdr dvb_usb_rtl28xxu 2>/dev/null || true
+ok "DVB-TV kernel driver blacklisted for RTL-SDR"
+
 # ── 2. Dependencies ─────────────────────────────────────────────────────────
 say "Installing dependencies"
 export DEBIAN_FRONTEND=noninteractive