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/test_tui_gateway_server.py

@@ -2397,7 +2397,7 @@ def test_config_set_model_waits_for_lazy_agent_before_switch(monkeypatch):
         target["agent"] = agent
         agent_ready.set()
 
-    def fake_apply(sid, target, raw):
+    def fake_apply(sid, target, raw, **kwargs):
         calls.append(("apply", sid, target.get("agent"), raw))
         if target.get("agent") is not agent:
             raise AssertionError("model switch ran before lazy agent was ready")
@@ -2424,7 +2424,7 @@ def test_config_set_model_uses_live_switch_path(monkeypatch):
     server._sessions["sid"] = _session()
     seen = {}
 
-    def _fake_apply(sid, session, raw):
+    def _fake_apply(sid, session, raw, **_kwargs):
         seen["args"] = (sid, session["session_key"], raw)
         return {"value": "new/model", "warning": "catalog unreachable"}
 
@@ -2442,6 +2442,74 @@ def test_config_set_model_uses_live_switch_path(monkeypatch):
     assert seen["args"] == ("sid", "session-key", "new/model")
 
 
+def test_config_set_model_requires_confirmation_for_expensive_model(monkeypatch):
+    class _Agent:
+        provider = "openrouter"
+        model = "old/model"
+        base_url = ""
+        api_key = "sk-or"
+        switched = False
+
+        def switch_model(self, **_kwargs):
+            self.switched = True
+
+    result = types.SimpleNamespace(
+        success=True,
+        new_model="openai/gpt-5.5-pro",
+        target_provider="openrouter",
+        api_key="sk-or",
+        base_url="https://openrouter.ai/api/v1",
+        api_mode="chat_completions",
+        warning_message="",
+        model_info=types.SimpleNamespace(
+            has_cost_data=lambda: True,
+            cost_input=25.0,
+            cost_output=125.0,
+        ),
+    )
+
+    agent = _Agent()
+    server._sessions["sid"] = _session(agent=agent)
+    monkeypatch.setattr(
+        "hermes_cli.model_switch.switch_model", lambda **_kwargs: result
+    )
+    monkeypatch.setattr(server, "_restart_slash_worker", lambda sid, session: None)
+    monkeypatch.setattr(server, "_emit", lambda *args, **kwargs: None)
+
+    resp = server.handle_request(
+        {
+            "id": "1",
+            "method": "config.set",
+            "params": {
+                "session_id": "sid",
+                "key": "model",
+                "value": "openai/gpt-5.5-pro --provider openrouter",
+            },
+        }
+    )
+
+    assert resp["result"]["confirm_required"] is True
+    assert "did you mean to select openai/gpt-5.5?" in resp["result"]["confirm_message"]
+    assert agent.switched is False
+
+    confirmed = server.handle_request(
+        {
+            "id": "2",
+            "method": "config.set",
+            "params": {
+                "session_id": "sid",
+                "key": "model",
+                "value": "openai/gpt-5.5-pro --provider openrouter",
+                "confirm_expensive_model": True,
+            },
+        }
+    )
+
+    assert confirmed["result"]["confirm_required"] is False
+    assert confirmed["result"]["value"] == "openai/gpt-5.5-pro"
+    assert agent.switched is True
+
+
 def test_config_set_model_global_persists(monkeypatch):
     class _Agent:
         provider = "openrouter"
@@ -3944,7 +4012,7 @@ def test_config_set_model_rejects_while_running(monkeypatch):
     """/model via config.set must reject during an in-flight turn."""
     seen = {"called": False}
 
-    def _fake_apply(sid, session, raw):
+    def _fake_apply(sid, session, raw, **_kwargs):
         seen["called"] = True
         return {"value": raw, "warning": ""}
 
@@ -3978,7 +4046,7 @@ def test_config_set_model_allowed_when_idle(monkeypatch):
     """Regression guard: idle sessions can still switch models."""
     seen = {"called": False}
 
-    def _fake_apply(sid, session, raw):
+    def _fake_apply(sid, session, raw, **_kwargs):
         seen["called"] = True
         return {"value": "newmodel", "warning": ""}