refactor(test): split docker e2e planner

scripts/e2e/session-runtime-context-docker.sh

@@ -17,6 +17,7 @@ cleanup() {
 trap cleanup EXIT
 
 docker_e2e_build_or_reuse "$IMAGE_NAME" session-runtime-context
+docker_e2e_harness_mount_args
 
 echo "Running session runtime context Docker E2E..."
 # Harness files are mounted read-only; the app under test comes from /app/dist.
@@ -24,7 +25,7 @@ set +e
 docker run --rm \
   --name "$CONTAINER_NAME" \
   -e COREPACK_ENABLE_DOWNLOAD_PROMPT=0 \
-  -v "$ROOT_DIR/scripts/e2e:/app/scripts/e2e:ro" \
+  "${DOCKER_E2E_HARNESS_ARGS[@]}" \
   "$IMAGE_NAME" \
   bash -lc 'set -euo pipefail; node --import tsx scripts/e2e/session-runtime-context-docker-client.ts' \
   >"$RUN_LOG" 2>&1