feat(llm-inference): Day 1 playbook for RTX 3090 vLLM stack on astro-orbiter

- nvidia-driver-595-open (already installed 2026-08-03, idempotent)
- Python venv + vLLM 0.26.0 (already installed, idempotent)
- Gemma 2 27B model download via HuggingFace hub
- systemd vllm-serve.service on port 8000
- Hermes provider integration on carousel-of-progress
- vault_hf_token added to group_vars/all/vault
- ansible.cfg: vault_password_file set to absolute path
- inventory: astro_orbiter group added

Run with: env -u ANSIBLE_VAULT_PASSWORD_FILE ansible-playbook -i inventory.yml playbooks/day1_deploy_llm_inference.yml

ansible/roles/llm-inference/tasks/serve.yml

@@ -0,0 +1,48 @@
+---
+# ------------------------------------------------------------------------------
+# FILE: roles/llm-inference/tasks/serve.yml
+# DESCRIPTION: Phase 5 — systemd vllm-serve service.
+#              Deploys the service unit, enables on boot, starts it, and
+#              health-checks the OpenAI-compatible API endpoint.
+# ------------------------------------------------------------------------------
+
+- name: Deploy vllm-serve systemd service unit
+  ansible.builtin.template:
+    src: vllm-serve.service.j2
+    dest: /etc/systemd/system/vllm-serve.service
+    owner: root
+    group: root
+    mode: "0644"
+  notify:
+    - reload systemd
+    - restart vllm-serve
+
+- name: Flush handlers to reload systemd before enabling service
+  ansible.builtin.meta: flush_handlers
+
+- name: Enable and start vllm-serve
+  ansible.builtin.systemd:
+    name: vllm-serve
+    state: started
+    enabled: true
+    daemon_reload: true
+
+- name: Wait for vLLM API to become available (model load can take ~60s)
+  ansible.builtin.uri:
+    url: "http://localhost:{{ llm_serve_port }}/health"
+    status_code: 200
+  register: vllm_health
+  retries: 30
+  delay: 10
+  until: vllm_health.status == 200
+
+- name: Smoke-test — list available models
+  ansible.builtin.uri:
+    url: "http://localhost:{{ llm_serve_port }}/v1/models"
+    status_code: 200
+    return_content: true
+  register: vllm_models
+
+- name: Print available models
+  ansible.builtin.debug:
+    msg: "vLLM serving: {{ vllm_models.json.data | map(attribute='id') | list }}"