This PR adds a detailed enhancement/audit plan for the
`decimo.decimal128` module, capturing cross-language comparisons,
identified correctness gaps, performance bottlenecks, and a prioritized
execution order.

**Changes:**
- Introduces a comprehensive design/audit document for `Decimal128`,
including a cross-language feature matrix.
- Documents key architectural concerns (notably the 2^96−1 coefficient
bound) and related performance implications.
- Lists suspected correctness/performance issues and proposes a phased
implementation plan.

…strings + Eliminate `mojo doc` warnings (#194)

This PR focuses on improving generated documentation by adding/expanding
docstrings across the TOML tokenizer/parser and the numeric types
(BigInt/BigUInt/BigDecimal/Decimal128/etc.), with the goal of
eliminating `mojo doc` warnings.

**Changes:**
- Added docstrings for structs, fields, constants, and many methods
across the codebase.
- Standardized docstring sections (Args/Returns/Parameters) in multiple
modules.
- Removed an unused error-message header constant from `errors.mojo`.

…e name and line number) (#195)

This PR refactors Decimo’s error handling to produce Python-style
tracebacks with ANSI coloring, and updates many call sites to raise
typed `DecimoError[...]` variants (e.g., `ValueError`, `OverflowError`)
with consistent metadata (message/function/previous error).

**Changes:**
- Reworked `DecimoError` formatting to mimic Python tracebacks,
including chained errors and ANSI colors.
- Updated many modules to raise structured `DecimoError` variants
instead of raw string `Error(...)` messages.
- Removed explicit `file=` parameters at many raise sites in favor of
auto-captured file/line via `call_location()`.

…or` type (#196)

This PR updates Decimo’s structured error type so that `DecimoError`
always includes a `message` and `function`, ensuring tracebacks
consistently show both fields (alongside auto-captured file/line).

**Changes:**
- Make `DecimoError.message` and `DecimoError.function` mandatory
(non-optional) and require them in `__init__`.
- Update error construction call sites across parsing, numeric parsing,
and numeric types to pass `message` + `function`.
- Convert a couple of previously string-raised errors to structured
`ValueError` instances to comply with the new contract.

…base to show correct error types (#199)

This PR updates docstring `Raises:` sections across Decimo to replace
generic `Error` entries with specific error types (e.g., `ValueError`,
`OverflowError`, `ZeroDivisionError`, `ConversionError`) so API
documentation more accurately reflects runtime behavior.

**Changes:**
- Standardized and expanded docstring `Raises:` sections across TOML
parsing, numeric parsing, and multiple numeric types (Decimal128/Big*).
- Replaced generic `Error`/`DecimoError` docstring entries with concrete
error types used by the implementation.
- Added missing `Raises:` sections to several functions that previously
had none.

…in error messages to ensure privacy at compilation (#200)

This PR updates Decimo’s error reporting to avoid exposing absolute file
system paths in error messages by shortening file paths captured via
`call_location()`.

**Changes:**
- Added a `_shorten_path()` helper to convert absolute paths into
`./src/...`, `./tests/...`, `./benches/...`, or filename-only paths.
- Updated `DecimoError.__init__` to store the shortened path instead of
the raw `call_location()` path.

…validation + custom usage line (#201)

This PR enhances the `decimo` CLI calculator’s argument parsing and
help/usage UX by leveraging newer ArgMojo features, and updates project
documentation/plans accordingly.

**Changes:**
- Add ArgMojo metadata to CLI options/flags (value names, numeric range
validation, help groups) and set a custom usage line.
- Enable ArgMojo negative-number passthrough for positional expressions.
- Update docs/plans to reflect ArgMojo v0.5.0 integration and adjust
pixi tasks for fetching ArgMojo source.

This PR updates the Decimo CLI argument parsing so expressions that
start with `-` (e.g., negative numbers / negative expressions) can be
passed as the positional `<EXPR>` more naturally, and documents/tests
the behavior.

**Changes:**
- Enable hyphen-prefixed values for the `expr` positional argument via
ArgMojo (`allow_hyphen=True`) and remove the older command-level
negative-number allowance.
- Expand CLI integration tests to cover negative expressions, mixed
option/positional ordering, and `--` separator cases.
- Add user-manual documentation for “Negative Expressions” and update
the CLI calculator plan checklist accordingly.

…de (#203)

This PR updates the Decimo CLI to avoid short-flag collisions with
negative expressions by uppercasing short options, and adds new stdin
(pipe) + file-based input modes for evaluating multiple expressions.

**Changes:**
- Uppercase short flags for formatting/computation options
(`-P/-S/-E/-D/-R`) and remove the `--pad` short flag to prevent
collisions with expressions like `-e`, `-pi`, `-sin(1)`.
- Add pipe mode (read/evaluate expressions from stdin, one per non-empty
non-comment line) and file mode (`-F/--file`).
- Extend integration/unit tests and update docs/changelog/plans for the
new CLI UX.

…n guide in user manual (#204)

This PR adds an interactive REPL mode to the Decimo CLI so `decimo` with
no arguments (and TTY stdin) launches an interactive calculator session,
aligning CLI UX with tools like `bc`. The PR also updates related CLI
docs/changelog and refines benchmark comparison logic.

**Changes:**
- Launch REPL when no expression/file is provided and stdin is a TTY;
add REPL implementation, prompt writer, and line-reading helper.
- Update CLI docs/changelog to describe REPL mode and revise the CLI
benchmark script to compare full-precision digits (with a guard digit).
- Normalize various docstrings to use single-backtick inline code
formatting.

This PR updates the documents and re-organize the "docs" folder.