Add comprehensive unit tests for src/main.rs to reach >80% coverage

[Copilot]

src/main.rs had only 1 unit test, leaving large portions of the binary's logic uncovered per SonarCloud's new code coverage report.

Description

Added 38 new unit tests directly in src/main.rs covering all previously untested functions and branches.

New test coverage

• Cli struct methods — get_project_path (default/custom), is_verbose, get_output, is_pretty, is_minify (via both --minify and --m2), is_aggressive_minify, get_transform_config (all flag combinations: keep_tests, keep_docs, no_expand_modules, minify, m2)
• minify_code() — empty input, single-line passthrough, multi-line joining, whitespace trimming, empty-line filtering
• aggressive_minify_code() — escaped string literals, char literals, empty input, trailing comma cleanup before }, ), ]
• should_rebuild() — Create/Modify/Remove events on .rs files (→ true); non-RS extensions, Access, Other, Any events, empty path list (→ false)
• display_bug_report_info() — smoke test for no panic
• format_with_rustfmt() — valid code and syntactically invalid code (returns None gracefully)

Type of change

• Bug fix
• New feature
• Documentation update
• Refactor
• Performance improvement
• Other (please describe): Test coverage improvement

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing tests pass locally with my changes
• I have updated the CHANGELOG.md

Screenshots (if applicable)

Additional context

All 39 tests (1 existing + 38 new) pass. Clippy reports no linting issues.

[MathieuSoysal]

@copilot It should be clippy compiliant and have good format