opentui(phase3): launcher integration — HERMES_TUI_ENGINE dual-engine

hermes --tui launches the native OpenTUI engine (Bun) when
HERMES_TUI_ENGINE=opentui (env) or display.tui_engine=opentui (config);
Ink stays the default and the shipping path is untouched.

- _resolve_tui_engine() (env > config > ink); refuses opentui on
  Windows/Termux (no Bun) -> falls back to ink with a notice.
- _make_opentui_argv() -> [bun, src/entry.real.tsx] (no build step).
- _bun_bin() with HERMES_BUN override.
- Branch at top of _make_tui_argv BEFORE _ensure_tui_node (Bun-only host
  must not bootstrap Node).
- Gate _launch_tui NODE_OPTIONS/--max-old-space-size on engine==ink (Bun
  is JSC; the V8 flag errors/ignores).

Verified end-to-end via tmux: real hermes --tui -> Bun -> OpenTUI ->
real Python gateway streamed a real reply. No-flag default still ink.

web/src/components/ModelPickerDialog.tsx

@@ -4,7 +4,6 @@ import { ListItem } from "@nous-research/ui/ui/components/list-item";
 import { Spinner } from "@nous-research/ui/ui/components/spinner";
 import { Input } from "@nous-research/ui/ui/components/input";
 import { Label } from "@nous-research/ui/ui/components/label";
-import { ConfirmDialog } from "@/components/ConfirmDialog";
 import type { GatewayClient } from "@/lib/gatewayClient";
 import { Check, Search, X } from "lucide-react";
 import { useEffect, useMemo, useRef, useState } from "react";
@@ -22,8 +21,9 @@ import { fuzzyRank } from "@/lib/fuzzy";
  * Two invocation modes:
  *
  * 1. Chat-session mode (ChatSidebar) — pass `gw` + `sessionId`. The picker
- *    loads options via `model.options` JSON-RPC and applies the choice via
- *    `config.set`, so expensive-model confirmation can happen before switch.
+ *    loads options via `model.options` JSON-RPC and emits the result as a
+ *    slash command string (`/model <model> --provider <slug> [--global]`)
+ *    through `onSubmit`, which the ChatPage pipes to `slashExec`.
  *
  * 2. Standalone mode (ModelsPage, Config settings) — pass a `loader` and
  *    `onApply`. The picker fetches options via the REST endpoint and calls
@@ -47,23 +47,6 @@ interface ModelOptionsResponse {
   providers?: ModelOptionProvider[];
 }
 
-interface ExpensiveModelConfirmResponse {
-  confirm_message?: string;
-  confirm_required?: boolean;
-  warning?: string;
-}
-
-interface ConfigSetResponse extends ExpensiveModelConfirmResponse {
-  value?: string;
-}
-
-interface PendingExpensiveConfirm {
-  message: string;
-  model: string;
-  persistGlobal: boolean;
-  provider: string;
-}
-
 interface Props {
   /** Chat-mode: when present, picker emits a slash command via onSubmit. */
   gw?: GatewayClient;
@@ -73,14 +56,10 @@ interface Props {
   /** Standalone-mode: when present (and onSubmit absent), picker calls onApply. */
   loader?(): Promise<ModelOptionsResponse>;
   onApply?(args: {
-    confirmExpensiveModel?: boolean;
     provider: string;
     model: string;
     persistGlobal: boolean;
-  }):
-    | Promise<ExpensiveModelConfirmResponse | void>
-    | ExpensiveModelConfirmResponse
-    | void;
+  }): Promise<void> | void;
 
   onClose(): void;
   title?: string;
@@ -111,8 +90,6 @@ export function ModelPickerDialog(props: Props) {
   const [query, setQuery] = useState("");
   const [persistGlobal, setPersistGlobal] = useState(alwaysGlobal);
   const [applying, setApplying] = useState(false);
-  const [pendingConfirm, setPendingConfirm] =
-    useState<PendingExpensiveConfirm | null>(null);
   const closedRef = useRef(false);
 
   // Load providers + models on open.
@@ -202,65 +179,16 @@ export function ModelPickerDialog(props: Props) {
 
   const canConfirm = !!selectedProvider && !!selectedModel && !applying;
 
-  const applySelection = async (
-    confirmExpensiveModel = false,
-    forced?: PendingExpensiveConfirm,
-  ) => {
-    const providerSlug = forced?.provider ?? selectedProvider?.slug ?? "";
-    const model = forced?.model ?? selectedModel;
-    const shouldPersistGlobal = forced?.persistGlobal ?? persistGlobal;
-
-    if (!providerSlug || !model || applying) return;
-
+  const confirm = async () => {
+    if (!canConfirm || !selectedProvider) return;
     if (standalone && onApply) {
       setApplying(true);
       try {
-        const result = await onApply({
-          confirmExpensiveModel,
-          provider: providerSlug,
-          model,
-          persistGlobal: shouldPersistGlobal,
+        await onApply({
+          provider: selectedProvider.slug,
+          model: selectedModel,
+          persistGlobal,
         });
-        if (result?.confirm_required) {
-          setPendingConfirm({
-            provider: providerSlug,
-            model,
-            persistGlobal: shouldPersistGlobal,
-            message:
-              result.confirm_message ||
-              result.warning ||
-              "This model has unusually high known pricing.",
-          });
-          return;
-        }
-        onClose();
-      } catch (e) {
-        setError(e instanceof Error ? e.message : String(e));
-      } finally {
-        setApplying(false);
-      }
-    } else if (gw && sessionId) {
-      setApplying(true);
-      try {
-        const global = shouldPersistGlobal ? " --global" : "";
-        const result = await gw.request<ConfigSetResponse>("config.set", {
-          confirm_expensive_model: confirmExpensiveModel,
-          key: "model",
-          session_id: sessionId,
-          value: `${model} --provider ${providerSlug}${global}`,
-        });
-        if (result?.confirm_required) {
-          setPendingConfirm({
-            provider: providerSlug,
-            model,
-            persistGlobal: shouldPersistGlobal,
-            message:
-              result.confirm_message ||
-              result.warning ||
-              "This model has unusually high known pricing.",
-          });
-          return;
-        }
         onClose();
       } catch (e) {
         setError(e instanceof Error ? e.message : String(e));
@@ -268,17 +196,14 @@ export function ModelPickerDialog(props: Props) {
         setApplying(false);
       }
     } else if (onSubmit) {
-      const global = shouldPersistGlobal ? " --global" : "";
-      onSubmit(`/model ${model} --provider ${providerSlug}${global}`);
+      const global = persistGlobal ? " --global" : "";
+      onSubmit(
+        `/model ${selectedModel} --provider ${selectedProvider.slug}${global}`,
+      );
       onClose();
     }
   };
 
-  const confirm = () => {
-    if (!canConfirm) return;
-    void applySelection();
-  };
-
   // Portal to document.body: the main dashboard column in App.tsx is
   // `relative z-2`, which creates a stacking context that traps fixed
   // descendants below the app sidebar (z-50). Without the portal this
@@ -355,12 +280,8 @@ export function ModelPickerDialog(props: Props) {
             onSelect={setSelectedModel}
             onConfirm={(m) => {
               setSelectedModel(m);
-              void applySelection(false, {
-                provider: selectedProvider?.slug ?? "",
-                model: m,
-                persistGlobal,
-                message: "",
-              });
+              // Confirm on next tick so state settles.
+              window.setTimeout(confirm, 0);
             }}
           />
         </div>
@@ -399,22 +320,6 @@ export function ModelPickerDialog(props: Props) {
           </div>
         </footer>
       </div>
-      <ConfirmDialog
-        open={!!pendingConfirm}
-        title="Expensive Model Warning"
-        description={pendingConfirm?.message}
-        destructive
-        confirmLabel="Switch anyway"
-        cancelLabel="Cancel"
-        loading={applying}
-        onCancel={() => setPendingConfirm(null)}
-        onConfirm={() => {
-          const pending = pendingConfirm;
-          if (!pending) return;
-          setPendingConfirm(null);
-          void applySelection(true, pending);
-        }}
-      />
     </div>,
     document.body,
   );