fix(gpu-box): drop gpu-promtail healthcheck — image has no curl/wget/nc

Promtail v3.0.0 ships a minimal alpine-ish image with only the
promtail binary. The original Mini compose's wget-based healthcheck
errored out with 'executable file not found' on every tick, marking
the container as 'unhealthy' for hours despite Loki actively
receiving logs from it. Restart-policy unless-stopped catches real
crashes anyway, so the healthcheck adds noise without value.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

infrastructure/docker-compose.gpu-box.yml

@@ -299,12 +299,7 @@ services:
     depends_on:
       loki:
         condition: service_started
-    healthcheck:
-      test: ['CMD', 'wget', '--no-verbose', '--tries=1', '--spider', 'http://127.0.0.1:9080/ready']
-      interval: 60s
-      timeout: 10s
-      retries: 3
-      start_period: 15s
+    # healthcheck disabled: promtail image has no curl/wget/nc; restart policy handles crashes
 
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