Rename the bin/dart_skills_lint.dart file to cli and update documenation.

[reidbaker]

I thought there were too many files named dart_skils_lint.* this removes one.

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.

[gemini-code-assist]

Code Review

This pull request renames the main CLI entry point from 'bin/dart_skills_lint.dart' to 'bin/cli.dart' across the project, including documentation, pubspec configuration, and all integration tests. I have no feedback to provide as the changes are consistent and correctly applied.