Release base-bash-libs v1.3.0

[codeforester]

Scope

Prepare and publish base-bash-libs v1.3.0 from the current Unreleased
changes.

Release checklist

• Update VERSION, the README version row/example, and CHANGELOG.md.
• Run ./tests/validate.sh and git diff --check.
• Run basectl release check|plan|notes for v1.3.0.
• Open and merge the release-preparation pull request.
• Publish the guarded v1.3.0 GitHub Release.
• Update and validate the Homebrew tap formula and any required bottles.
• Update Base's full-SHA dependency pin and validate the downstream checkout.
• Record release and downstream links, then clean up release branches.

The release contract is declared in base_manifest.yaml and the detailed
sequence is documented in docs/release-process.md.

[codeforester]

Released as https://github.com/basefoundry/base-bash-libs/releases/tag/v1.3.0. Release commit: 5e52e79. Homebrew handoff: basefoundry/homebrew-base#78. Base dependency pin: basefoundry/base#1651, merged as 586015a8d7ca777df22637cdb64e2248c6b5d0ef.