SPL Meter 0.4.3: a failed capture-tool build must not park the listener forever

Same deadlock the Timers module hit live on AB (fixed there in 1.5.1):
start() skipped scheduling its retry while a build was in flight, and
ensureCaptureBinary's onReady only fires on build SUCCESS. A failed
build therefore left the listener waiting forever on a callback that
never comes — "Building the capture tool…" indefinitely — and a binary
scp'd in from outside (the required path on AB, whose CLT cannot
compile) was never picked up without a module remount.

onReady stays as the fast path; the 30-second retry is now armed in
every not-ready state, so a failed build keeps re-checking and an
externally supplied binary is found within half a minute.

Reproduced pre-fix (build fails at 0s, binary copied in at 3s, still
untouched at 38s) and verified post-fix (retry at 30s spawns it).
spl-capture --selftest unchanged against the IEC 61672 table.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

modules/spl-meter/module.json

@@ -1,7 +1,7 @@
 {
   "id": "spl-meter",
   "name": "SPL Meter",
-  "version": "0.4.2",
+  "version": "0.4.3",
   "proddash": ">=1.5.0",
   "description": "Calibrated sound level, Leq and RTA from an audio input on this machine",
   "permissions": [