feat: introduce very_good.yaml for param configuration

[unicoderbot]

Warning

The coding agent reported this implementation is incomplete.
very_good.yaml is wired up for the test command only; other commands and the pubspec.yaml very_good: key remain future work, and the local analyzer/test suite could not run due to a Dart SDK version mismatch (3.11.5 available, 3.12.0 required by pubspec).

This PR has been opened as a draft. Review the diff against the original issue before marking it ready for review.

Summary

Adds support for configuring CLI test parameters through a very_good.yaml configuration file at the project root. This allows developers to maintain consistent configuration across local and CI environments without manually repeating flags.

Changes

• Introduces VeryGoodConfig loading from very_good.yaml files
• Updates FlutterTestOptions.parse() to accept config with proper precedence (CLI args override config file values)
• Adds comprehensive test coverage for config loading and precedence rules
• Implements graceful error handling for malformed config files
• Documents new feature in test command documentation

Configuration Example

# very_good.yaml
test:
  min-coverage: 100
  exclude-coverage: "**/*.g.dart"
  report-on:
    - lib/
  dart-define:
    - FLAVOR=development

Supported options include: concurrency, coverage, min-coverage, show-uncovered, exclude-tags, tags, exclude-coverage, collect-coverage-from, optimization, update-goldens, fail-fast, dart-define, dart-define-from-file, platform, report-on, run-skipped, flavor, and timeout.

Precedence

• CLI arguments take precedence over config file values
• Config file values are used as defaults when flags aren't explicitly passed

Closes #360

[marcossevilla]

@vgvbot investigate and fix CI. additionally add an e2e test that provides a very_good.yaml file and verifies the file is parsed correctly and overrides the configuration based on it

[unicoderbot]

On it, I'll address the review comments and push the changes.

• Preparing environment
  • Cloning repository
  • Setting up dev environment
• Reviewing feedback
• Working on changes
• Pushing updates

I've pushed changes to address the feedback.