fix: add log rotation to docker-compose to prevent disk fill

Test output now goes to container stdout via Stdio::inherit, so logs
grow fast. Cap at 50MB with 3 rotated files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker/docker-compose.yml

@@ -108,6 +108,14 @@ services:
       retries: 3
       start_period: 10s
 
+    # Log rotation – test output goes to stdout via Stdio::inherit,
+    # so container logs grow fast without rotation.
+    logging:
+      driver: json-file
+      options:
+        max-size: "50m"
+        max-file: "3"
+
     # Use tini as PID 1 to reap zombie child processes.
     # Without this, grandchild processes (esbuild, cargo, etc.) spawned by
     # npm/cargo during worktree setup and gate checks become zombies.