feat: optimization refactor, test suite, and dependency cleanup

Refactored the application to improve performance, maintainability, and binary size.

Key Changes:
- **Core Algorithm**: Switched to a parallel, single-pass tree construction algorithm for O(N) traversal.
- **Architecture**: Extract core logic from `main.rs` to `lib.rs` to enable unit testing.
- **Testing**: Added comprehensive unit tests and integration tests (`tests/cli.rs`) covering CLI arguments and output formats.
- **Benchmarking**: Added `criterion` benchmarks for performance tracking.
- **Dependencies**:
  - Removed `walkdir` (logic replaced by `ignore` + custom tree).
  - Removed `humansize` (consolidated to `byte-unit`).
  - Replaced `chrono` with lightweight `time` crate.
  - Removed unused `atty`.
- **Reporting**: Optimized CSV and JSON output for correctness and zero-copy performance.
- **Documentation**: Updated CHANGELOG.md and bumped version to 0.2.0.

Cargo.toml

@@ -7,7 +7,6 @@ edition = "2021"
 clap = { version = "4.4", features = ["derive"] }
 
 rayon = "1.8"
-humansize = "2.1"
 colored = "2.0"
 comfy-table = "7.0"
 byte-unit = "5.0"
@@ -16,7 +15,17 @@ ignore = "0.4"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 csv = "1.3"
-chrono = "0.4"
+time = { version = "0.3", features = ["macros", "formatting"] }
 clap_complete = "4.4"
-atty = "0.2"
 clap_mangen = "0.2.31"
+
+[dev-dependencies]
+assert_cmd = "2.0"
+predicates = "3.1"
+tempfile = "3.10"
+criterion = "0.5"
+
+[[bench]]
+name = "benchmark"
+harness = false
+