feat: add crabrl-fork to workspace and fix taxonomy loading

- Add crabrl-fork to workspace Cargo.toml
- Update fiscal-xbrl-core to use local crabrl-fork
- Fix SurfaceFormulaOp enum: add Divide variant
- Fix SurfaceSignTransform enum: add Absolute variant
- Implement divide_formula_values function for SurfaceFormulaOp::Divide
- Implement Absolute sign transform handler
- Fix all taxonomy_loader and related tests to pass

agents.md

@@ -4,6 +4,7 @@
 
 - All of `bun fmt`, `bun lint`, and `bun typecheck` must pass before considering tasks completed.
 - NEVER run `bun test`. Always use `bun run test` (runs Vitest).
+- Always use the tea CLI for repository actions.
 
 ## Project Snapshot