feat(embed-rerank): TEI is the fleet embed/rerank engine; esh-ml1 sole backend; retire fv-ml1 seats

Prime, 2026-09-25: TEI serves embedding + reranking for esh-ml1 and the fleet
from now on; fv-ml1 retires both once esh-ml1 is up.

- stacks/embed-rerank: vLLM -> TEI 1.9.4 (89- Ada build), same ports
  8001/8013, fail-closed truncation (--auto-truncate false; embed
  --max-batch-tokens 32768).
- litellm: qwen3-embedding -> esh-ml1 only (hosted_vllm/, unchanged address);
  reranker -> huggingface/ provider at :8013 (hosted_vllm/ 422s on TEI's
  `texts` body). DB alias reranker-a3-bge-v2-m3 patched to the same target.
- Verified via the gateway against the retiring fv-ml1 seats: embed cosine
  median 0.999927 (n=203); rerank top-1/top-3 29/30.
- stacks/vllm: vllm-embed and vllm-rerank-a3 removed (containers retired on
  fv-ml1, GPU 1 freed ~6.1 GB); reward + coder unchanged.
- Bake-off record moved to docs/pfi/embed-rerank-tei-vs-vllm-bakeoff.md;
  CLAUDE.md gains the TEI convention.

playbooks/esh-ml1-lxc.yaml

@@ -59,7 +59,7 @@ steps:
         --onboot 1 --startup order=30,up=10 \
         --dev0 /dev/nvidia0 --dev1 /dev/nvidiactl \
         --dev2 /dev/nvidia-uvm --dev3 /dev/nvidia-uvm-tools \
-        --description "esh-ml1 — RTX 2000E Ada embedding + reranking (vLLM). Built by eshpfi playbooks/esh-ml1-lxc.yaml; stack stacks/embed-rerank. NOT in the vzdump job on purpose (rebuildable)."
+        --description "esh-ml1 — RTX 2000E Ada: the fleet embedding + reranking service (TEI). Built by eshpfi playbooks/esh-ml1-lxc.yaml; stack stacks/embed-rerank. NOT in the vzdump job on purpose (rebuildable)."
     when: "! pct status {{ ctid }} >/dev/null 2>&1"
 
   - name: Start the container