chore: prepare v0.4.2 release

[abhiksark]

Summary

Prepares dev for the immutable v0.4.2 release after the .gitignore, manifest-error, and update-precedence fixes landed. Package metadata and dated release notes now agree on 0.4.2, while public status pages use PyPI as the live version source instead of hardcoded stale release numbers.

Release guidance now uses a version-neutral expected-output example. Contributor and roadmap pages route current work to the active issue tracker.

Tests

• python -m pytest -q: 185 passed
• Python 3.9 isolated suite: 185 passed; curriculum and installed-wheel smoke passed
• Python 3.10 isolated suite: 185 passed; curriculum and installed-wheel smoke passed
• pythonlings --root tests/fixtures/passing_curriculum verify: passing1 and passing2 passed
• python -m mkdocs build --strict: passed
• python -m build: built pythonlings-0.4.2.tar.gz and pythonlings-0.4.2-py3-none-any.whl
• Clean 0.4.2 wheel install: version, init, list, solution, and reset flows passed
• Installed wheel patch smokes: .gitignore preservation/idempotency, current-workspace update precedence, no-create failures, and friendly invalid-manifest exit status passed
• Code review: complete (20260817-release-metadata); no actionable findings remain

Screenshots

Not applicable. This change updates release metadata and documentation only.

Checklist

• Updated docs when behavior changed
• Existing regression and installed-wheel tests cover the included behavior
• Verified python -m pytest -q

Post-Deploy Monitoring & Validation

• Logs: watch the GitHub Actions publish workflow for ERROR, tag/version mismatch, build failure, and trusted-publishing failure messages.
• Surfaces: verify the GitHub Release asset list and the PyPI 0.4.2 Files and provenance views.
• Healthy signals: the annotated v0.4.2 tag resolves to the dev to main promotion commit; the workflow succeeds; PyPI exposes one sdist and one wheel with provenance; a clean install reports pythonlings 0.4.2.
• Failure trigger: stop if any tag, release, artifact, package version, or ancestry check disagrees. Do not move the tag or overwrite PyPI; publish corrections as v0.4.3.
• Window and owner: the maintainer validates continuously from tag creation through the successful clean-environment install.

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