gt - Mini CLI calculator with REPL

Age	Commit message (Collapse)	Author
2026-03-25	docs: Add SPDX license headers to all .go source files	Paul Buetow
	- Added 'SPDX-License-Identifier: MIT' and 'Copyright (c) 2026 Paul Buetow' headers - Files updated: 24 .go files across cmd/gt/, internal/calculator/, internal/repl/, internal/rpn/ The MIT license from LICENSE file is reflected in all source files.
2026-03-24	feat: Add RPN mode, rational number support, and improve REPL	Paul Buetow
	- Add RPN (Reverse Polish Notation) calculator with stack-based operations - Support precise rational number calculations using big.Rat - Implement chain of responsibility pattern for command handling - Add auto-completion for built-in commands - Add history persistence with configurable max entries - Support standard operators: +, -, , /, ^, %, lg, log, ln - Support hyper operators: [+], [-], [*], [/], [^], [%], [lg], [log], [ln] - Support stack manipulation: dup, swap, pop, show - Support variable assignments and management - Add rat mode for switching between float64 and rational calculations - Refactor calculator to return Calculation struct with formatting - Add proper version support (v0.3.0) All changes follow Go best practices with comprehensive test coverage.