Status line: move model segment to the right cluster (model, cost, time)

Left group keeps the where-am-I identity (host, path, git, pr); the right
cluster carries what's-running (model) plus cost and elapsed time, painted
in array order. context_pct verified to hoist into the inline meter spacer
regardless of array position. Docs + changelog updated.

agent/config.yml

@@ -110,11 +110,11 @@ statusLine:
     - vim
     - mode
     - hostname
-    - model
     - path
     - git
     - pr
   rightSegments:
+    - model
     - cost
     - context_pct
     - time_spent