Prevent build-and-test container name collisions in XPU PR workflow

[Copilot]

PR Test (XPU) was intermittently failing in build-and-test before tests started because docker run reused a static container name on a shared self-hosted runner. This change isolates container identity per workflow run/attempt to remove cross-run conflicts.

• Root cause

  • Run container used hardcoded --name ci_sglang_xpu, which conflicts when a prior container with that name still exists (e.g., retries/overlap on the same runner).

• Workflow update

  • Added job-level env var:
    • CI_CONTAINER_NAME: ci_sglang_xpu_${{ github.run_id }}_${{ github.run_attempt }}
  • Replaced all direct ci_sglang_xpu references with ${CI_CONTAINER_NAME}.

• Scope of replacement

  • docker run --name ...
  • all docker exec ...
  • all docker cp ...
  • cleanup docker rm -f ...

env:
  CI_CONTAINER_NAME: ci_sglang_xpu_${{ github.run_id }}_${{ github.run_attempt }}

# examples
docker run -dt --name "${CI_CONTAINER_NAME}" ...
docker exec "${CI_CONTAINER_NAME}" ...
docker cp "${CI_CONTAINER_NAME}":/path/in/container ./local.log
docker rm -f "${CI_CONTAINER_NAME}" || true