Initial commit: Developer Tools MVP with visual editor

- Complete React app with 7 developer tools
- JSON Tool with visual structured editor
- Serialize Tool with visual structured editor
- URL, Base64, CSV/JSON, Beautifier, Diff tools
- Responsive navigation with dropdown menu
- Dark/light mode toggle
- Mobile-responsive design with sticky header
- All tools working with copy/paste functionality

node_modules/@isaacs/cliui/build/index.d.cts

@@ -0,0 +1,43 @@
+interface UIOptions {
+    width: number;
+    wrap?: boolean;
+    rows?: string[];
+}
+interface Column {
+    text: string;
+    width?: number;
+    align?: "right" | "left" | "center";
+    padding: number[];
+    border?: boolean;
+}
+interface ColumnArray extends Array<Column> {
+    span: boolean;
+}
+interface Line {
+    hidden?: boolean;
+    text: string;
+    span?: boolean;
+}
+declare class UI {
+    width: number;
+    wrap: boolean;
+    rows: ColumnArray[];
+    constructor(opts: UIOptions);
+    span(...args: ColumnArray): void;
+    resetOutput(): void;
+    div(...args: (Column | string)[]): ColumnArray;
+    private shouldApplyLayoutDSL;
+    private applyLayoutDSL;
+    private colFromString;
+    private measurePadding;
+    toString(): string;
+    rowToString(row: ColumnArray, lines: Line[]): Line[];
+    // if the full 'source' can render in
+    // the target line, do so.
+    private renderInline;
+    private rasterize;
+    private negatePadding;
+    private columnWidths;
+}
+declare function ui(opts: UIOptions): UI;
+export { ui as default };