I need a brand-new “ClassicalDataGrid” plugin that mirrors the Finos Perspective Data Grid (github.com/finos/perspective) but replaces its tree-style pivot with the traditional Excel-like layout. The work targets the browser only; my current tech stack combines Rust or C++ for the heavy lifting with a JS/HTML/CSS front end, so the final package has to slot cleanly into that toolchain. Core requirements • Classical pivot format: multiple row-header columns shown side-by-side instead of a hierarchical tree. • Each header level must expand/collapse individually, with an option to repeat or suppress labels (“repeated label true/false”). • Export the grid exactly as displayed to CSV and XLSX. • Allow users to hide or reveal subtotals without disturbing underlying calculations. • Preserve every other Perspective Data Grid UI feature—filtering, sorting, styling, virtual scrolling, etc.—unchanged. Deliverables 1. Source code for the plugin (Rust/C++ module if compiled, plus JS bindings and front-end components). 2. Build/installation instructions and minimal demo page to prove it works in a modern browser. 3. Documentation of public APIs and any extra configuration flags you introduce. 4. A short test suite or reproducible steps that confirm the expand/collapse logic, export accuracy, and subtotal toggle. Acceptance criteria • Compiles and runs locally with one command (npm/yarn/cargo/cmake, as applicable). • Matches Perspective’s performance for datasets up to 1 M rows. • CSV/XLSX exports open in Excel with identical row/column arrangement. • Delivered within 10 calendar days from project start. • Group BY columns as per i photo mentioned Feel free to suggest minor API tweaks if they make the integration cleaner, but the visual and functional spec above is fixed.