tui-double-buffer: Implement smart differential rendering with terminal abstraction

- Create Terminal interface abstracting stdin/stdout operations for dependency injection
- Implement ProcessTerminal for production use with process.stdin/stdout
- Implement VirtualTerminal using @xterm/headless for accurate terminal emulation in tests
- Fix TypeScript imports for @xterm/headless module
- Move all component files to src/components/ directory for better organization
- Add comprehensive test suite with async/await patterns for proper render timing
- Fix critical TUI differential rendering bug when components grow in height
  - Issue: Old content wasn't properly cleared when component line count increased
  - Solution: Clear each old line individually before redrawing, ensure cursor at line start
- Add test verifying terminal content preservation and text editor growth behavior
- Update tsconfig.json to include test files in type checking
- Add benchmark test comparing single vs double buffer performance

The implementation successfully reduces flicker by only updating changed lines
rather than clearing entire sections. Both TUI implementations maintain the
same interface for backward compatibility.

packages/tui/src/text-component.ts

@@ -1,104 +0,0 @@
-import type { Component, ComponentRenderResult, Padding } from "./tui.js";
-
-export class TextComponent implements Component {
-	private text: string;
-	private lastRenderedLines: string[] = [];
-	private padding: Required<Padding>;
-
-	constructor(text: string, padding?: Padding) {
-		this.text = text;
-		this.padding = {
-			top: padding?.top ?? 0,
-			bottom: padding?.bottom ?? 0,
-			left: padding?.left ?? 0,
-			right: padding?.right ?? 0,
-		};
-	}
-
-	render(width: number): ComponentRenderResult {
-		// Calculate available width after horizontal padding
-		const availableWidth = Math.max(1, width - this.padding.left - this.padding.right);
-		const leftPadding = " ".repeat(this.padding.left);
-
-		// First split by newlines to preserve line breaks
-		const textLines = this.text.split("\n");
-		const lines: string[] = [];
-
-		// Add top padding
-		for (let i = 0; i < this.padding.top; i++) {
-			lines.push("");
-		}
-
-		// Process each line for word wrapping
-		for (const textLine of textLines) {
-			if (textLine.length === 0) {
-				// Preserve empty lines with padding
-				lines.push(leftPadding);
-			} else {
-				// Word wrapping with ANSI-aware length calculation
-				const words = textLine.split(" ");
-				let currentLine = "";
-				let currentVisibleLength = 0;
-
-				for (const word of words) {
-					const wordVisibleLength = this.getVisibleLength(word);
-					const spaceLength = currentLine ? 1 : 0;
-
-					if (currentVisibleLength + spaceLength + wordVisibleLength <= availableWidth) {
-						currentLine += (currentLine ? " " : "") + word;
-						currentVisibleLength += spaceLength + wordVisibleLength;
-					} else {
-						if (currentLine) {
-							lines.push(leftPadding + currentLine);
-						}
-						currentLine = word;
-						currentVisibleLength = wordVisibleLength;
-					}
-				}
-
-				if (currentLine) {
-					lines.push(leftPadding + currentLine);
-				}
-			}
-		}
-
-		// Add bottom padding
-		for (let i = 0; i < this.padding.bottom; i++) {
-			lines.push("");
-		}
-
-		const newLines = lines.length > 0 ? lines : [""];
-
-		// Check if content changed
-		const changed = !this.arraysEqual(newLines, this.lastRenderedLines);
-
-		// Always cache the current rendered lines
-		this.lastRenderedLines = [...newLines];
-
-		return {
-			lines: newLines,
-			changed,
-		};
-	}
-
-	setText(text: string): void {
-		this.text = text;
-	}
-
-	getText(): string {
-		return this.text;
-	}
-
-	private arraysEqual(a: string[], b: string[]): boolean {
-		if (a.length !== b.length) return false;
-		for (let i = 0; i < a.length; i++) {
-			if (a[i] !== b[i]) return false;
-		}
-		return true;
-	}
-
-	private getVisibleLength(str: string): number {
-		// Remove ANSI escape codes and count visible characters
-		return (str || "").replace(/\x1b\[[0-9;]*m/g, "").length;
-	}
-}