fix(model): require confirmation for expensive model selections

Rebased onto current main and re-ported across the restructured
surfaces: model flows now thread confirm_provider/base_url/api_key
through hermes_cli/model_setup_flows.py, the Discord picker lives in
plugins/platforms/discord/adapter.py, and the web dashboard picker
applies chat-mode switches via config.set so the expensive-model
confirmation can ride the response.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/hermes_cli/test_terminal_menu_fallbacks.py

@@ -2,6 +2,7 @@
 cannot initialize (e.g. non-TTY, curses unavailable, terminal error)."""
 
 import subprocess
+from types import SimpleNamespace
 
 from hermes_cli.config import load_config, save_config
 
@@ -24,6 +25,46 @@ def test_prompt_model_selection_falls_back_on_menu_runtime_error(monkeypatch):
     assert selected == "model-b"
 
 
+def test_prompt_model_selection_requires_expensive_confirmation(monkeypatch, capsys):
+    from hermes_cli.auth import _prompt_model_selection
+
+    monkeypatch.setattr("hermes_cli.curses_ui.curses_radiolist", _raise_menu)
+    monkeypatch.setattr(
+        "hermes_cli.model_cost_guard.expensive_model_warning",
+        lambda *_args, **_kwargs: SimpleNamespace(message="EXPENSIVE MODEL WARNING"),
+    )
+    responses = iter(["1", "n"])
+    monkeypatch.setattr("builtins.input", lambda _prompt="": next(responses))
+
+    selected = _prompt_model_selection(
+        ["openai/gpt-5.5-pro"],
+        confirm_provider="nous",
+    )
+
+    out = capsys.readouterr().out
+    assert selected is None
+    assert "EXPENSIVE MODEL WARNING" in out
+
+
+def test_prompt_model_selection_allows_confirmed_expensive_model(monkeypatch):
+    from hermes_cli.auth import _prompt_model_selection
+
+    monkeypatch.setattr("hermes_cli.curses_ui.curses_radiolist", _raise_menu)
+    monkeypatch.setattr(
+        "hermes_cli.model_cost_guard.expensive_model_warning",
+        lambda *_args, **_kwargs: SimpleNamespace(message="EXPENSIVE MODEL WARNING"),
+    )
+    responses = iter(["1", "y"])
+    monkeypatch.setattr("builtins.input", lambda _prompt="": next(responses))
+
+    selected = _prompt_model_selection(
+        ["openai/gpt-5.5-pro"],
+        confirm_provider="nous",
+    )
+
+    assert selected == "openai/gpt-5.5-pro"
+
+
 def test_prompt_reasoning_effort_falls_back_on_menu_runtime_error(monkeypatch):
     from hermes_cli.main import _prompt_reasoning_effort_selection