feat(llm-inference-multimodel): codify Phi-3.5-mini + Llama-3.1-8B GGUF staging (t_730f9584)

Adds idempotent, data-driven GGUF staging for the two new router models on
astro-orbiter alongside the production Qwen3.6-35B-A3B-UD-Q4_K_S. Both files
were already staged live (byte-exact); this commit codifies them in Ansible so
future re-runs and any new model adds are version-controlled and audit-friendly.

Changes:
- roles/llm-inference-multimodel/tasks/stage_model.yml (NEW)
  Idempotent per-model task: stat -> exact byte-size guard -> conditional
  get_url -> ownership/mode ensure -> notify router restart handler only on
  actual download. Loops from models.yml; nothing hardcoded.

- roles/llm-inference-multimodel/tasks/models.yml
  Appends the stage_model.yml loop (tagged: models) after the existing Qwen3.6
  download tasks. Data driven from host_vars/astro-orbiter/vars.yml.

- roles/llm-inference-multimodel/defaults/main.yml
  Adds llm_staged_models: [] default (empty = safe no-op for hosts with no
  staged model list defined).

- roles/llm-inference-multimodel/handlers/main.yml
  Adds 'restart llama-server-router on new GGUF' handler. Only fires when
  stage_model.yml performs an actual download or corrects ownership/mode.
  Normal idempotent re-runs (files already correct) do NOT fire this handler.

- host_vars/astro-orbiter/vars.yml
  Adds llm_staged_models list with the two new models:
    * Phi-3.5-mini-instruct-Q8_0.gguf (4,061,222,688 bytes,
      bartowski/Phi-3.5-mini-instruct-GGUF)
    * Meta-Llama-3.1-8B-Instruct-Q4_K_M.gguf (4,920,739,232 bytes,
      bartowski/Meta-Llama-3.1-8B-Instruct-GGUF)

- playbooks/day1_deploy_llm_inference_multimodel.yml
  Updates header comment: removes stale 'Semaphore broken' note, documents
  the correct execution channel (Semaphore template
  llm_inference_multimodel_stage_models, --tags models).

- group_vars/all/semaphore.yml
  Adds llm_inference_multimodel_stage_models template entry (config-as-code).
  Template is scoped to --tags models explicitly. Phase 4 (verify) is
  EXCLUDED: verify.yml starts llama-server-qwen on :8002, which would collide
  with the production llama-server-router.service already running on :8002.

Semaphore template created via API: project 1 / template id 19.
Execution: triggered immediately after this commit via Semaphore REST API.

ansible/playbooks/day1_deploy_llm_inference_multimodel.yml

@@ -11,9 +11,13 @@
 #   # or scope to specific phases:
 #   ansible-playbook -i inventory.yml playbooks/day1_deploy_llm_inference_multimodel.yml --tags discover
 #
-# KNOWN GAP (2026-08-05): Semaphore is currently broken; this is being run
-# via direct ansible-playbook as an accepted interim stopgap. Retarget
-# through Semaphore once it's repaired.
+# EXECUTION CHANNEL (2026-08-12, War Machine): run via the Semaphore template
+# "llm_inference_multimodel_stage_models" (scoped to --tags models). Do NOT
+# run this via direct ansible-playbook or ad-hoc ssh/curl/systemctl — all
+# homelab inference changes go through Ansible roles executed by Semaphore for
+# audit/visibility. Phase 1 (models) is idempotent: it only downloads/stages a
+# GGUF when missing or size-mismatched, and only restarts the router when a new
+# GGUF is detected (normal re-runs that find the files correct touch nothing).
 #
 # Phases (see roles/llm-inference-multimodel/README.md for detail):
 #   0. discover  — read-only; confirm existing Gemma service management