Add --no-progress flag to suppress real-time progress display

[Chemaclass]

📚 Description

Add a new --no-progress flag that suppresses real-time progress display during test execution, showing only the final summary. This addresses Issue #503.

When enabled, bashunit hides:

• Per-test output (pass/fail messages or dots)
• File headers ("Running tests/...")
• Hook completion messages
• Spinner during parallel execution

The final summary with test counts and results is still displayed.

This is useful for:

• CI/CD pipelines where streaming output causes issues
• Log-restricted environments
• Reducing output noise when only the final result matters

🔖 Changes

• Add --no-progress CLI flag in src/main.sh
• Add BASHUNIT_NO_PROGRESS environment variable support in src/env.sh
• Add bashunit::env::is_no_progress_enabled helper function
• Suppress per-test output in src/state.sh when flag is enabled
• Suppress file headers in src/runner.sh when flag is enabled
• Suppress hook completion messages in src/console_results.sh when flag is enabled
• Suppress spinner in src/runner.sh when flag is enabled
• Add help text for the new option in src/console_header.sh
• Add comprehensive acceptance tests in tests/acceptance/bashunit_no_progress_test.sh
• Update documentation in docs/command-line.md and docs/configuration.md
• Update CHANGELOG.md with the new feature

✅ To-do list

• I updated the CHANGELOG.md to reflect the new feature or fix
• I updated the documentation to reflect the changes