docs: date approved 0.1.13 release notes - #150

Purpose

Record the approved 0.1.13 release date in release/changelog.json and regenerate CHANGELOG.md with the existing generator. No source, dependency, comparison or workflow changes.

Verification

• The last qualified main 2f2cb62 has all applicable checks passing.
• Canonical preflight confirms no conflicting remote tag, GitHub release or PyPI version.
• Focused changelog contracts, generator check and all commit hooks are required before merge; exact-head hosted qualification will also be required.
• Existing native and timing evidence is reused unchanged.

AI assistance

Codex prepared the date update, ran the existing generator and checks, and reviewed the resulting diff.