WIP: Migrate dart_skills_lint to google/skills_lint.dart

[reidbaker-agent]

Ignore this pr for now.
dart_skills_lint is moving to its own repo. This pr was one of a few used to validate the migration guide. Nothing to do until the new repo location is public.

The agent authored description is actually pretty spot on.

• @reidbaker

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Sample prompts

ok lets validate the migration guide. The current workspace is the devtools repo. validate_skills_test.dart uses the old dart_skills_lint package. In a sub agent Using only the migration guide and a local path override to our new repo /Users/reidbaker/.gemini/jetski/brain//scratch/skills_lint.dart migrate dev tools to use the new package. If the sub agent runs into issues it cant solve then we need to update the migration guide and try again.

ok open a draft pr against devtools with the changes but using the not yet public github url. The pr will not work in that state because the repo is not public but it will once that changes.

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Agent authored pr description
Draft PR to migrate the skills linter dependency to the newly graduated repository.

Note: This PR will fail CI until the google/skills_lint.dart repository is fully pushed and made accessible. It is created now to prepare for the switch.