Improve repository About and README search positioning

[codeforester]

Summary

Update the repository-facing description so base-bash-libs is easier to discover through GitHub search and package consumers can quickly understand that it is a standalone Bash helper library.

Scope

• Lead with search-friendly Bash standard library language in the top README.
• Keep the Base extraction context, but make independent consumption clear.
• Use natural keywords for the existing helper areas: logging, error handling, command execution, file edits, Git helpers, string utilities, temp paths, cleanup hooks, and imports.

Acceptance Criteria

• README intro describes base-bash-libs as a reusable/sourceable Bash standard library.
• README continues to make clear that Base is not required to consume the package.
• Change is documentation-only and passes a whitespace diff check.