test(e2e): Docker daemon unavailable in orchestrated worker

[moncher-dev]

The Docker E2E runner cannot start in the issue #901 worker environment because Docker Compose cannot reach /var/run/docker.sock.

Reproduction:

./e2e/run-standalone-project-e2e.sh

Observed twice on 2026-09-06: Cannot connect to the Docker daemon at unix:///var/run/docker.sock before the scenario executes.

This blocks Docker black-box validation but does not indicate a product-code failure.

[moncher-dev]

Duplicate of #914 — same condition (Docker daemon unreachable at /var/run/docker.sock inside the Symphony worker environment, black-box gate exits on its prerequisite check). Consolidated there and assigned to @hojinzs as a host/execution-environment decision.