feat: add xhigh thinking level support for gpt-5.2 and gpt-5.2-codex

- Add XHIGH_MODELS constant and getAvailableThinkingLevels() to AgentSession
- Update ThinkingSelectorComponent to accept availableLevels parameter
- Both shift+tab cycling and /thinking command now show xhigh for supported models
- Update types.ts documentation to list supported models

packages/coding-agent/src/modes/interactive/components/thinking-selector.ts

@@ -3,28 +3,40 @@ import { Container, type SelectItem, SelectList } from "@mariozechner/pi-tui";
 import { getSelectListTheme } from "../theme/theme.js";
 import { DynamicBorder } from "./dynamic-border.js";
 
+const LEVEL_DESCRIPTIONS: Record<ThinkingLevel, string> = {
+	off: "No reasoning",
+	minimal: "Very brief reasoning (~1k tokens)",
+	low: "Light reasoning (~2k tokens)",
+	medium: "Moderate reasoning (~8k tokens)",
+	high: "Deep reasoning (~16k tokens)",
+	xhigh: "Maximum reasoning (~32k tokens)",
+};
+
 /**
  * Component that renders a thinking level selector with borders
  */
 export class ThinkingSelectorComponent extends Container {
 	private selectList: SelectList;
 
-	constructor(currentLevel: ThinkingLevel, onSelect: (level: ThinkingLevel) => void, onCancel: () => void) {
+	constructor(
+		currentLevel: ThinkingLevel,
+		availableLevels: ThinkingLevel[],
+		onSelect: (level: ThinkingLevel) => void,
+		onCancel: () => void,
+	) {
 		super();
 
-		const thinkingLevels: SelectItem[] = [
-			{ value: "off", label: "off", description: "No reasoning" },
-			{ value: "minimal", label: "minimal", description: "Very brief reasoning (~1k tokens)" },
-			{ value: "low", label: "low", description: "Light reasoning (~2k tokens)" },
-			{ value: "medium", label: "medium", description: "Moderate reasoning (~8k tokens)" },
-			{ value: "high", label: "high", description: "Deep reasoning (~16k tokens)" },
-		];
+		const thinkingLevels: SelectItem[] = availableLevels.map((level) => ({
+			value: level,
+			label: level,
+			description: LEVEL_DESCRIPTIONS[level],
+		}));
 
 		// Add top border
 		this.addChild(new DynamicBorder());
 
 		// Create selector
-		this.selectList = new SelectList(thinkingLevels, 5, getSelectListTheme());
+		this.selectList = new SelectList(thinkingLevels, thinkingLevels.length, getSelectListTheme());
 
 		// Preselect current level
 		const currentIndex = thinkingLevels.findIndex((item) => item.value === currentLevel);

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -1301,6 +1301,7 @@ export class InteractiveMode {
 		this.showSelector((done) => {
 			const selector = new ThinkingSelectorComponent(
 				this.session.thinkingLevel,
+				this.session.getAvailableThinkingLevels(),
 				(level) => {
 					this.session.setThinkingLevel(level);
 					this.updateEditorBorderColor();