llm-inference-multimodel: fix verify.yml losing Gemma-stop gate when run with --tags verify

discover.yml sets llm_existing_gemma_unit_found, but main.yml imports each
phase file with import_tasks + a distinct per-phase tag. Tags on
import_tasks apply to the whole file, so --tags verify (a supported,
documented way to re-run just this phase) skips discover.yml, leaving
the fact undefined. The stop task's 'default(false)' silently no-op'd,
so re-running verify alone against a host with Gemma still running would
start both new instances on top of it -- the OOM this task exists to
prevent.

Fix: gather service_facts and set the fact locally in verify.yml too,
only when not already defined, so the guard works regardless of which
tags were selected.

ansible/roles/llm-inference-multimodel/tasks/verify.yml

@@ -28,6 +28,28 @@
 # works unchanged. If no such unit was found, this is a no-op and the
 # original WARNING from discover.yml (any Gemma process running outside
 # systemd) still stands as a human decision point.
+#
+# BUGFIX (found in production): main.yml imports each phase file with
+# import_tasks + a per-phase tag (tags: [discover], tags: [verify], ...).
+# Tags on import_tasks apply to every task inside that file, so running
+# `--tags verify` alone — a normal, supported way to re-run just this
+# phase per the header comment in main.yml — skips discover.yml entirely.
+# llm_existing_gemma_unit_found was then simply undefined, and the
+# `| default(false)` on this task's `when:` silently swallowed that,
+# defeating the whole point of this fix: --tags verify against a host
+# with Gemma still running would go straight to starting both new
+# services on top of it, the exact OOM scenario this task exists to
+# prevent. Gather the fact locally here too so this task is correct
+# regardless of which tags were requested.
+- name: Gather service facts (systemd unit inventory) — ensure available even if discover.yml's tag wasn't selected
+  ansible.builtin.service_facts:
+  when: llm_existing_gemma_unit_found is not defined
+
+- name: Determine whether a systemd unit matching the existing Gemma service exists (if not already known from discover.yml)
+  ansible.builtin.set_fact:
+    llm_existing_gemma_unit_found: "{{ (llm_existing_gemma_service_name_guess + '.service') in ansible_facts.services }}"
+  when: llm_existing_gemma_unit_found is not defined
+
 - name: Stop pre-existing Gemma llama-server before starting new instances (avoid double VRAM usage / OOM)
   ansible.builtin.systemd:
     name: "{{ llm_existing_gemma_service_name_guess }}"