Show reasoning effort in the model's own vocabulary (K3: max, not xhigh)

The welcome and prompt model labels (and /effort's 'current' hint)
rendered the canonical internal level name, so K3 at its default effort
showed 'K3 (xhigh)' even though the server's vocabulary for that level is
'max' (live /models think_efforts: low/high/max).

New ModelState::reasoning_effort_display() resolves the current effort
through the model's own effort menu (option id whose value matches),
falling back to the canonical name only when the model has no entry for
the level. All three display sites route through it; test pins the K3
mapping (Xhigh → 'max', Low → 'low', no-menu-entry → canonical).

crates/codegen/kigi-tui/src/acp/model_state.rs

@@ -204,6 +204,22 @@ impl ModelState {
         parse_reasoning_efforts_meta(info.meta.as_ref()).unwrap_or_else(legacy_effort_options)
     }
 
+    /// Display token for the current reasoning effort, in the MODEL's own
+    /// vocabulary: the menu option id whose value matches (e.g. K3 spells
+    /// `Xhigh` as `max`), falling back to the canonical name only when the
+    /// model has no menu entry for it. Displays must never leak the internal
+    /// canonical spelling for a level the server names differently.
+    pub fn reasoning_effort_display(&self) -> Option<String> {
+        let effort = self.reasoning_effort?;
+        let display = self
+            .reasoning_effort_options()
+            .into_iter()
+            .find(|opt| opt.value == effort)
+            .map(|opt| opt.id)
+            .unwrap_or_else(|| effort.as_str().to_owned());
+        Some(display)
+    }
+
     /// Map a typed/selected effort token to its canonical value for the current
     /// model. Accepts a menu option id (case-insensitive) or a canonical level
     /// that appears as a **value** in that model's menu. Levels the model does
@@ -479,6 +495,30 @@ mod tests {
         assert_eq!(opts[1].description.as_deref(), Some("Max"));
     }
 
+    /// K3 spells `Xhigh` as `max` (live /models `think_efforts`): every
+    /// display surface must show the model's own vocabulary, never the
+    /// internal canonical name.
+    #[test]
+    fn reasoning_effort_display_uses_model_vocabulary() {
+        let mut state = state_with_meta(Some(serde_json::json!({
+            "supportsReasoningEffort": true,
+            "reasoningEfforts": [
+                { "id": "low", "value": "low", "label": "Low" },
+                { "id": "high", "value": "high", "label": "High" },
+                { "id": "max", "value": "xhigh", "label": "Max" },
+            ],
+        })));
+        state.reasoning_effort = Some(ReasoningEffort::Xhigh);
+        assert_eq!(state.reasoning_effort_display().as_deref(), Some("max"));
+        state.reasoning_effort = Some(ReasoningEffort::Low);
+        assert_eq!(state.reasoning_effort_display().as_deref(), Some("low"));
+        // No menu entry for the level → canonical fallback (never hide it).
+        state.reasoning_effort = Some(ReasoningEffort::Medium);
+        assert_eq!(state.reasoning_effort_display().as_deref(), Some("medium"));
+        state.reasoning_effort = None;
+        assert_eq!(state.reasoning_effort_display(), None);
+    }
+
     #[test]
     fn reasoning_effort_options_gate_first_empty_when_unsupported() {
         // No current model → empty.