Allow individual skills to be specified in dart_skills_lint.yaml

[reidbaker-agent]

Fixes #166
add changelog entry adding to the definition-of-done
Add dart format and analyze to reidbaker-agent persona.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

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[gemini-code-assist]

Code Review

This pull request introduces support for configuring individual skills via the individual_skills key in dart_skills_lint.yaml, allowing path-specific rule severity mapping without relying on root directory scanning. It refactors ConfigParser to use a shared helper _parseConfigList (renaming DirectoryConfig to LintTargetConfig), adds validation to prevent overlapping paths between directories and individual skills, and updates documentation and tests accordingly. Feedback on this PR highlights a critical bug in entry_point.dart where passing effectiveIndividualSkillPaths to _getEffectiveSkillDirPaths inadvertently skips the fallback logic for configured directories. Additionally, it is recommended to improve the error messages in _parseConfigList by dynamically labeling entries instead of hardcoding 'Directory entry' to avoid confusing users when errors occur under the individual_skills configuration.

[reidbaker]

/gemini-review