Add dotenv file operations

CHANGELOG.md

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+# Changelog
+
+All notable changes to this project are documented in this file.
+
+This project follows [Semantic Versioning](https://semver.org/) and the format is loosely based on [Keep a Changelog](https://keepachangelog.com/).
+
+## 0.0.3 (2026-01-13)
+
+### Added
+
+- Dotenv file operations (CLI): `validate`, `copy`, `format`/`reorder`, and `annotate`.
+- Round-trippable dotenv parsing for file ops (preserves comments/blank lines) with issue reporting that includes line/column.
+- Library API exports for file ops: `validateEnvFile`, `copyEnvFileKeys`, `formatEnvFile`, `annotateEnvFile`.
+- Test coverage for file operations.
+
+### Changed
+
+- Package version bumped to `0.0.3`.
+
+## 0.0.2 (2026-01-12)
+
+### Added
+
+- Match operators for boolean checks beyond strict equality:
+  - `exists`, `is_empty`, `is_equal`, `partial_match_prefix`, `partial_match_suffix`, `partial_match_regex`, `is_number`, `is_boolean`, `is_string`.
+- CLI support for `match --op <op>`.
+- Library support for `EnvSitter.matchKey()` / `EnvSitter.matchKeyBulk()` with matcher operators.
+- More tests for matcher operators.
+
+### Changed
+
+- Expanded CLI docs and output contract guidance in `README.md`.
+- Added a reference to `envsitter-guard` in documentation.
+
+## 0.0.1
+
+### Added
+
+- Initial public release.
+- CLI commands: `keys`, `fingerprint`, `match`, `match-by-key`, `scan`.
+- Library API: `EnvSitter` with safe key listing, deterministic fingerprints (HMAC-SHA-256 + pepper), and outside-in matching.
+- Support for dotenv sources via local file and external command.