Release mnemostack 1.3.0

[Udjin79]

Summary

• bump the canonical project and package versions from 1.2.0 to 1.3.0
• close the changelog section for the multi-field lexical retrieval work and real-Qdrant CI coverage on 2026-07-27
• add a release-metadata regression test requiring the package version to have a dated changelog entry

Release scope

This is a minor release because the changes merged after 1.2.0 add public, backward-compatible functionality: configurable multi-field lexical arms, per-field fusion weights, named retriever arms, and corresponding CLI, MCP, HTTP, diagnostics, and CI behavior.

Validation

• pytest -q — 1495 passed, 10 skipped
• ruff check .
• mypy src
• python -m build
• twine check on both the wheel and sdist
• clean-wheel installation in a temporary virtual environment
• package metadata, mnemostack.__version__, and mnemostack --version all report 1.3.0
• inspected wheel contents for the CLI, config, retriever, vector-store, metadata, and entry-point files

Audit

Re-read the release diff independently after validation, including version-source drift, changelog placement/date, package metadata, unintended tracked build artifacts, and release-scope regressions. The audit found no behavioral or security changes in this release-only diff. The added changelog-version regression test guards the release metadata invariant that was previously checked only manually.

This PR does not create a tag, GitHub Release, or PyPI publication.