Prepare base-bash-libs v1.4.0 release

[codeforester]

Summary

• prepare base-bash-libs for the v1.4.0 release
• update VERSION and the README release references to 1.4.0
• move the current logging, security, and compatibility notes from
  Unreleased into the dated 1.4.0 changelog section

Validation

• ./tests/validate.sh — 321 BATS tests plus the logging smoke and examples
  passed
• git diff --check
• basectl release check --version 1.4.0 --manifest base_manifest.yaml
• basectl release plan --version 1.4.0 --manifest base_manifest.yaml
• basectl release notes --version 1.4.0 --manifest base_manifest.yaml

Release handoff

After merge, publish with the guarded basectl release publish flow, verify
the annotated tag and GitHub Release, then complete the required Homebrew
formula/bottle and Base full-SHA dependency handoffs documented in
docs/release-process.md.

Tracks #197

Checklist

• Branch name follows <category>/<issue>-<YYYYMMDD>-<slug>.
• Pull request is scoped to one issue.
• Pull request body explains what changed and how it was validated.
• Documentation and changelog metadata are aligned with VERSION.
• GitHub Actions checks pass.