fix(coding-agent): clamp thinking level to model capabilities

- setThinkingLevel() now clamps xhigh to high when model doesn't support it
- Model changes automatically re-clamp the current thinking level
- Fixed /model command to use session.setModel() instead of agent.setModel()
- Footer and editor border color update after model/thinking changes

Closes #253

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

@@ -1172,6 +1172,7 @@ export class InteractiveMode {
 		if (newLevel === null) {
 			this.showStatus("Current model does not support thinking");
 		} else {
+			this.footer.updateState(this.session.state);
 			this.updateEditorBorderColor();
 			this.showStatus(`Thinking level: ${newLevel}`);
 		}
@@ -1184,6 +1185,7 @@ export class InteractiveMode {
 				const msg = this.session.scopedModels.length > 0 ? "Only one model in scope" : "Only one model available";
 				this.showStatus(msg);
 			} else {
+				this.footer.updateState(this.session.state);
 				this.updateEditorBorderColor();
 				const thinkingStr =
 					result.model.reasoning && result.thinkingLevel !== "off" ? ` (thinking: ${result.thinkingLevel})` : "";
@@ -1310,6 +1312,7 @@ export class InteractiveMode {
 				this.session.getAvailableThinkingLevels(),
 				(level) => {
 					this.session.setThinkingLevel(level);
+					this.footer.updateState(this.session.state);
 					this.updateEditorBorderColor();
 					done();
 					this.showStatus(`Thinking level: ${level}`);
@@ -1379,11 +1382,17 @@ export class InteractiveMode {
 				this.ui,
 				this.session.model,
 				this.settingsManager,
-				(model) => {
-					this.agent.setModel(model);
-					this.sessionManager.saveModelChange(model.provider, model.id);
-					done();
-					this.showStatus(`Model: ${model.id}`);
+				async (model) => {
+					try {
+						await this.session.setModel(model);
+						this.footer.updateState(this.session.state);
+						this.updateEditorBorderColor();
+						done();
+						this.showStatus(`Model: ${model.id}`);
+					} catch (error) {
+						done();
+						this.showError(error instanceof Error ? error.message : String(error));
+					}
 				},
 				() => {
 					done();