Refactor repositories.go tools to use NewTool pattern with ToolDependencies

Convert all 18 tool functions in repositories.go to use the new NewTool helper
pattern with typed ToolDependencies, isolating type assertions to a single
location and improving code maintainability.

Functions converted:
- GetCommit, ListCommits, ListBranches
- CreateOrUpdateFile, CreateRepository, GetFileContents
- ForkRepository, DeleteFile, CreateBranch, PushFiles
- ListTags, GetTag, ListReleases, GetLatestRelease, GetReleaseByTag
- ListStarredRepositories, StarRepository, UnstarRepository

This is part of a stacked PR series to systematically migrate all tool
files to the new pattern.

Co-authored-by: Adam Holt <oholt@github.com>

Author: SamMorrowDrums