fix(i18n): improve null handling in interpolation

src/i18n/index.ts

@@ -35,7 +35,8 @@ export class I18n {
 
 	private interpolate(template: string, params: TranslationParams): string {
 		return template.replace(/\{\{(\w+)\}\}/g, (match, key) => {
-			return params[key]?.toString() || match
+			// Use != null to check for both null and undefined, allow empty strings
+			return params[key] != null ? params[key].toString() : match
 		})
 	}
 

src/ui/Panel.ts

@@ -426,10 +426,7 @@ export class Panel {
 	#updateHistory(): void {
 		const steps = this.#state.getAllSteps()
 
-		this.#historySection.innerHTML = steps
-			.slice(-10) // Only show last 10 items
-			.map((step) => this.#createHistoryItem(step))
-			.join('')
+		this.#historySection.innerHTML = steps.map((step) => this.#createHistoryItem(step)).join('')
 
 		// Scroll to bottom to show latest records
 		this.#scrollToBottom()
@@ -491,7 +488,7 @@ export class Panel {
 		const stepLabel = this.#pageAgent.i18n.t('ui.panel.step', {
 			number: step.stepNumber.toString(),
 			time,
-			duration: durationText,
+			duration: durationText || '', // Explicitly pass empty string to replace template
 		})
 
 		return `