fix(lab): make Asterisk logs usable — drop ANSI codes and healthcheck noise

Logging was configured correctly and shipping to Loki, but the stream was
useless: measured at 100% healthcheck chatter, with every line wrapped in ANSI
escape codes. The real SIP events were there and completely buried.

Three causes, each masking the next:

- asterisk.conf was written in the first lab commit with `nocolor = yes` and
  never mounted, so the setting had no effect. Now mounted. It was also
  overriding [directories] and runuser/rungroup, which the image sets up
  correctly itself — removed, since overriding them risks breaking the
  container for no gain.

- The image's command is `-vvvdddf`: verbosity 3 and debug 3 forced on the
  command line, which overrides both asterisk.conf and logger.conf. Overridden
  in compose to drop -v and -d; warnings and errors still log, and verbosity
  is raisable at runtime when tracing a call.

- The actual source: the image's healthcheck makes ~7 separate `asterisk -rx`
  connections every 30s, and Asterisk logs a connect/disconnect pair for each.
  Replaced with a single check on a 60s interval, and the check now runs
  `pjsip show transports` rather than `core show version` — that fails when
  Asterisk is up but unconfigured, which is exactly the state that produced a
  "healthy" container with no SIP stack on first deploy.

logger.conf drops both `notice` and `verbose`, which is where those pairs
arrive.

Verified on galatea: noise down from ~48 to 8 lines per two minutes (-83%),
zero ANSI codes in Loki, 90% of the stream now signal, container still
healthy, transport and dialplan intact.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/lab/dialplan/asterisk.conf

@@ -1,24 +1,17 @@
 ; Minimal Asterisk core config for the lab.
-[directories](!)
-astetcdir => /etc/asterisk
-astmoddir => /usr/lib/asterisk/modules
-astvarlibdir => /var/lib/asterisk
-astdbdir => /var/lib/asterisk
-astkeydir => /var/lib/asterisk
-astdatadir => /var/lib/asterisk
-astagidir => /var/lib/asterisk/agi-bin
-astspooldir => /var/spool/asterisk
-astrundir => /var/run/asterisk
-astlogdir => /var/log/asterisk
-astsbindir => /usr/sbin
-
+;
+; Deliberately does NOT set [directories] or runuser/rungroup: the image's
+; compiled-in defaults are correct, and it runs as the `asterisk` user via a
+; USER directive. Overriding either risks breaking the container for no gain
+; (an earlier version of this file did both).
 [options]
-; Log to stdout so Docker's json-file driver captures it and Alloy ships it.
-; A file-based log inside the container would be invisible to Loki.
+; Log to stdout so Docker's json-file driver captures it and Alloy ships it
+; to Loki. A file-based log inside the container would be invisible.
 verbose = 3
 debug = 0
+; No ANSI colour. Asterisk colourises the console by default and the escape
+; codes travel through Docker into Loki, where every line arrives wrapped in
+; \x1b[0;30m — unreadable in Grafana and awkward to filter on. This setting
+; lives here, not in logger.conf, and only takes effect if this file is
+; actually mounted into the container.
 nocolor = yes
-dumpcore = no
-; Never run as root inside the container.
-runuser = asterisk
-rungroup = asterisk