feat(llm-serving): give the chat model a stable client-facing name

poimen-memory will address `reasoning-long-predictor`, and the plan replaces
vLLM with candle-vllm underneath. Without an indirection, that handoff changes
a hostname the client is pinned to, and the ingest cutover has a window where
the name is wrong.

This Service is that indirection. It selects the vLLM reasoning pod today. The
handoff becomes a selector edit with no client change, so poimen-memory's
LLM_CHAT_BASE stays fixed across both engines.

Two ports, both verified through the Service from inside the poimen-memory pod:

  80   -> 8080   HTTP 200 in 0.0057s   matches every other predictor Service and
                                       poimen-memory's LLM_CHAT_BASE, which has
                                       no port in the URL
  8080 -> 8080   HTTP 200 in 0.0182s   the container port, the only port the two
                                       NetworkPolicies permit, and the port the
                                       handoff readiness check uses

Existing predictor Services publish port 80 only, so a curl to :8080 on one of
them fails to connect. Publishing both here means neither caller has to know
which convention the other follows.

Verified the selector resolves to the intended pod and nothing else: one
endpoint, 10.244.4.171, which is reasoning-predictor-59b67d5f5d-6mbbb.

Residual state, deliberately: /v1/models through this Service returns
['reasoning'], not ['reasoning-long'], because the second served name lands in
the previous commit and ArgoCD selfHeal reverts a live patch to a tracked pod
spec. Both names appear after this branch merges and syncs.

Not deleted and recreated at handoff. A delete drops the ClusterIP, and a
client that cached the name across the gap fails until it re-resolves.

k8s/apps/llm-serving/kustomization.yaml

@@ -19,6 +19,9 @@ resources:
   # model-name change. reasoning.yaml below can be dropped once that host change lands.
   - coder.yaml
   - reasoning.yaml
+  # Stable client-facing name for the chat model. poimen-memory points at this Service,
+  # so the vLLM -> candle-vllm handoff is a selector edit here and no client change.
+  - reasoning-long-service.yaml
   # ornith is retired: its InferenceService still reports Ready=True while running zero
   # replicas, because desired equals available at 0. Its manifest was never committed,
   # so it is left unmanaged and is not listed here. Delete the CR when convenient.

k8s/apps/llm-serving/reasoning-long-service.yaml

@@ -0,0 +1,43 @@
+# Stable client-facing name for the chat model, deliberately decoupled from the
+# process that currently serves it.
+#
+# poimen-memory addresses this Service, not a pod and not an InferenceService. That
+# means the vLLM -> candle-vllm handoff changes only this file's selector. The client
+# config never changes again, so the ingest cutover has no window in which the host
+# name is wrong.
+#
+# Two ports on purpose:
+#   - 80    matches every other predictor Service in this namespace, and matches
+#           poimen-memory's LLM_CHAT_BASE, which carries no port number.
+#   - 8080  is the container port. It is also the only port llm-serving-ingress and
+#           poimen-memory-llm-egress permit, and the port the handoff readiness check
+#           uses. Publishing it directly avoids a port translation that is easy to get
+#           wrong in a curl.
+#
+# The selector names the vLLM reasoning pod today. To hand off, replace the three
+# selector labels with candle-vllm's pod labels and nothing else. Do not delete and
+# recreate this Service: a delete drops the ClusterIP, and a client that cached the
+# name during the gap will fail until it re-resolves.
+apiVersion: v1
+kind: Service
+metadata:
+  name: reasoning-long-predictor
+  namespace: llm-serving
+  labels:
+    app.kubernetes.io/part-of: llm-serving
+    app: reasoning-long-predictor
+spec:
+  type: ClusterIP
+  selector:
+    app.kubernetes.io/name: llm-reasoning
+    component: predictor
+    serving.kserve.io/inferenceservice: reasoning
+  ports:
+    - name: http
+      protocol: TCP
+      port: 80
+      targetPort: 8080
+    - name: http-8080
+      protocol: TCP
+      port: 8080
+      targetPort: 8080