fix(compose): add OMNIBIOAI_WORK_DIR env var for correct path translation

Passes WORK_DIR into the workbench container so executors can resolve
/app/work/ paths correctly via the updated _to_host_path() function.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: man4ish

docker-compose.yml

@@ -225,6 +225,7 @@ services:
       OPENAI_API_KEY: ${OPENAI_API_KEY:-}
       OMNIBIOAI_TES_URL: http://tes:8081
       OMNIBIOAI_HOST_APP_PREFIX: ${WORKSPACE_HOST}
+      OMNIBIOAI_WORK_DIR: ${WORK_DIR}
       OMNI_OBJECT_STORAGE_DIR: /app/work/objects
       OMNI_OBJECT_REGISTRY_PATH: /app/work/object_registry.json
       OMNIBIOAI_RUNS_ROOT: /app/work/runs