6a8fecd03e
Cherry-picked and integrated the best code from 105 parallel epic branches into a clean workspace structure: - calcpad-engine/: Core Rust crate with lexer, parser, AST, interpreter, types, FFI (C ABI), pipeline, error handling, span tracking, eval context (from epic/1-5 base) - calcpad-engine/src/number.rs: Arbitrary precision arithmetic via dashu crate, WASM-compatible, exact decimals (from epic/1-4) - calcpad-engine/src/sheet_context.rs: SheetContext with dependency graph, dirty tracking, circular detection, cheap clone (from epic/1-8) - calcpad-wasm/: Thin WASM wrapper crate via wasm-bindgen, delegates to calcpad-engine (from epic/1-6) - Updated .gitignore for target/, node_modules/, build artifacts - Fixed run-pipeline.sh for macOS compat and CalcPad phases 79 tests passing across workspace.