Declare the AI owner, and let every node borrow its model over the mesh

vv_is_ai_host() was `=== 'host1'`, which made a physical fact — that is where the
GPU is — look like a rule. AI_OWNER_HOST declares it, so the card can move to a
rebuilt host3 or a friend's spare.

The gate was also doing two jobs. Assistant docks and findings strips now ask
whether a model is reachable, so a node without a GPU gets them by borrowing;
the AI tab asks whether this is the owner, because that page carries the bug
reports, the index and the model configuration — the surface where the
vocabulary assumes you built the mesh.

Resolution is local, then owner, then anyone else declaring a model, pinned once
it answers. Pinned rather than re-derived per call: a mesh that re-decides every
request eventually decides differently mid-conversation, and a chat whose second
turn lands on another machine has no history there. Cleared only on a transport
failure, and only when there is somewhere else to go — a single-node mesh whose
model is down should say so, not report AI as unconfigured.

Deployment/master.conf.template

@@ -1707,6 +1707,11 @@
 
 # ━━━ AI Master Switch ━━━
 # Fail-closed: anything other than the literal "true" means off.
+# Which node runs the model, the retrieval index and the bug store. Every other node borrows it
+# over the mesh, so a box without a GPU still gets the assistant — it just does not get the AI tab.
+# Defaults to host1 when unset or malformed: whoever builds the mesh is host1.
+    AI_OWNER_HOST="host1"
+
     AI_ENABLED=false
     AI_CONNECT_TIMEOUT=5            # seconds — probe when resolving which node has Ollama
     AI_REQUEST_TIMEOUT=240          # seconds — must clear a cold model load