fix(#2338): prevent known model + Auto effort from falling through to auto row

The whale-route fallback in the picker constructor used show_custom_model_row
as the gate for selecting the 'auto' vs custom row, but a known DeepSeek model
(e.g. v4-pro) paired with ReasoningEffort::Auto would not match any whale route
yet still have show_custom_model_row=false — silently landing on the auto row
and replacing the explicit model with 'auto' on apply.

Key the fallback on whether the initial model is actually 'auto' instead.
When a whale-route fallback selects the custom row, ensure show_custom_model_row
is set to true so the row is visible in the picker UI.

Also:
- Add regression test: known-model + Auto effort must not fall to auto row.
- Clean up picker_auto_model_forces_auto_effort_on_apply: remove manual
  mutations of selected_model_idx / selected_effort_idx which whale-route
  mode never reads.
- Rename Porpoise → Beluga per #2016, which excludes porpoises from the
  user-facing whale pool.

crates/tui/src/tui/model_picker.rs

@@ -2,7 +2,7 @@
 //!
 //! For DeepSeek providers the picker shows whale-sized routes — model + effort
 //! combinations sorted largest → fastest with friendly whale-species labels
-//! (Blue Whale, Fin Whale, …, Porpoise).  A single ↑/↓ selection sets both
+//! (Blue Whale, Fin Whale, …, Beluga).  A single ↑/↓ selection sets both
 //! model and effort at once.  The "auto" option is always available; custom
 //! (unrecognised) model ids appear as a separate row.
 //!
@@ -110,23 +110,30 @@ impl ModelPickerView {
 
         // When showing whale routes, find the matching route by position in the array
         // (not by sort_order, which happens to match today but is semantically wrong).
-        let selected_route_idx = if show_whale_routes {
-            WHALE_ROUTES
+        let (selected_route_idx, show_custom_model_row) = if show_whale_routes {
+            let idx = WHALE_ROUTES
                 .iter()
                 .position(|r| {
                     r.model.eq_ignore_ascii_case(&initial_model) && r.effort == normalized
                 })
                 .unwrap_or_else(|| {
-                    // No matching whale route — fall back to "auto" (standard model)
-                    // or the custom row (unrecognized model).
-                    if show_custom_model_row {
-                        WHALE_ROUTES.len() + 1 // custom model row
-                    } else {
+                    // No matching whale route — key the fallback on whether the
+                    // current model is actually "auto", not on show_custom_model_row.
+                    // Otherwise a known DeepSeek model (e.g. v4-pro) paired with
+                    // ReasoningEffort::Auto silently falls through to the "auto" row
+                    // and replaces the explicit model on apply.
+                    if initial_model.eq_ignore_ascii_case("auto") {
                         WHALE_ROUTES.len() // "auto" row
+                    } else {
+                        WHALE_ROUTES.len() + 1 // custom model row
                     }
-                })
+                });
+            // When the whale-route fallback selected the custom row, ensure it is
+            // visible so the user can see their current model in the picker.
+            let show_custom = show_custom_model_row || idx == WHALE_ROUTES.len() + 1;
+            (idx, show_custom)
         } else {
-            0
+            (0, show_custom_model_row)
         };
 
         Self {
@@ -621,12 +628,7 @@ mod tests {
         app.auto_model = true;
         app.reasoning_effort = ReasoningEffort::Off;
 
-        let mut view = ModelPickerView::new(&app);
-        view.selected_model_idx = 0;
-        view.selected_effort_idx = PICKER_EFFORTS
-            .iter()
-            .position(|effort| *effort == ReasoningEffort::Max)
-            .expect("max effort row");
+        let view = ModelPickerView::new(&app);
 
         assert_eq!(view.resolved_model(), "auto");
         assert_eq!(view.resolved_effort(), ReasoningEffort::Auto);
@@ -747,6 +749,24 @@ mod tests {
         assert_eq!(view.resolved_effort(), ReasoningEffort::Max);
     }
 
+    #[test]
+    fn whale_routes_known_model_auto_effort_does_not_fall_to_auto() {
+        // Regression: a known DeepSeek model paired with ReasoningEffort::Auto
+        // must NOT fall through to the "auto" row — that would silently replace
+        // the explicit model with "auto" on apply.
+        let (mut app, _lock) = create_test_app();
+        app.model = "deepseek-v4-pro".to_string();
+        app.auto_model = false;
+        app.reasoning_effort = ReasoningEffort::Auto;
+        let view = ModelPickerView::new(&app);
+        // Should fall to custom row (WHALE_ROUTES.len() + 1), not auto row.
+        assert_eq!(view.selected_route_idx, WHALE_ROUTES.len() + 1);
+        assert_eq!(view.resolved_model(), "deepseek-v4-pro");
+        assert_eq!(view.resolved_effort(), ReasoningEffort::Auto);
+        // The custom row must be visible so the user sees their current model.
+        assert!(view.show_custom_model_row);
+    }
+
     #[test]
     fn whale_routes_auto_effort_maps_to_fallback_row() {
         let (mut app, _lock) = create_test_app();

crates/tui/src/tui/whale_routes.rs

@@ -12,7 +12,7 @@
 //! 3. Sperm Whale  — Pro + no thinking
 //! 4. Humpback     — Flash + max thinking
 //! 5. Minke Whale  — Flash + high thinking
-//! 6. Porpoise     — Flash + no thinking (smallest, fastest)
+//! 6. Beluga       — Flash + no thinking (smallest, fastest)
 //!
 //! Unknown or non-DeepSeek models fall back to the raw model id without
 //! fake whale labeling.
@@ -80,7 +80,7 @@ pub const WHALE_ROUTES: &[WhaleRoute] = &[
         description: "Fast model, moderate reasoning — tool execution, read-only scouting",
     },
     WhaleRoute {
-        label: "Porpoise",
+        label: "Beluga",
         model: "deepseek-v4-flash",
         effort: ReasoningEffort::Off,
         sort_order: 5,
@@ -135,10 +135,10 @@ mod tests {
     }
 
     #[test]
-    fn lookup_porpoise_for_flash_off() {
+    fn lookup_beluga_for_flash_off() {
         let route = WhaleRoute::for_model_effort("deepseek-v4-flash", ReasoningEffort::Off)
-            .expect("porpoise route exists");
-        assert_eq!(route.label, "Porpoise");
+            .expect("beluga route exists");
+        assert_eq!(route.label, "Beluga");
         assert_eq!(route.sort_order, 5);
     }
 
@@ -163,7 +163,7 @@ mod tests {
     #[test]
     fn by_sort_order_finds_correct_routes() {
         assert_eq!(WhaleRoute::by_sort_order(0).unwrap().label, "Blue Whale");
-        assert_eq!(WhaleRoute::by_sort_order(5).unwrap().label, "Porpoise");
+        assert_eq!(WhaleRoute::by_sort_order(5).unwrap().label, "Beluga");
         assert!(WhaleRoute::by_sort_order(99).is_none());
     }