feat(workspace,settings): model menu chip in the composer, compact settings panels

The workspace home's composer takes ONE Model chip (ModelMenu: model list
plus Effort) and moves AI Router / Permission / Local-New worktree into the
row under it; Settings drops the General-page cost card and export row,
PricingSettings and the empty states are compacted for settings panels.

client/src/pages/AiToolConfig.tsx

@@ -47,14 +47,14 @@ function DefaultModel({ toolId, saved }: { toolId: string; saved: string }) {
     <div className="space-y-2">
       <p className="text-xs text-fg-muted">{t("toolTab.defaultModelHint")}</p>
       <div className="flex flex-wrap items-start gap-2">
-        <div className="min-w-[16rem] flex-1">
+        <div className="w-72 max-w-full">
           <ModelPicker value={value} onChange={setValue} tool={toolId} />
         </div>
         <button
           type="button"
           onClick={save}
           disabled={value === saved}
-          className="btn-ghost text-xs disabled:opacity-50"
+          className="btn-primary text-xs disabled:opacity-50"
         >
           {t("toolTab.saveDefaultModel")}
         </button>