Streamline the CLI repository entry point

[rmcdaniel]

Summary

• replace the prerelease-heavy root README with a concise stable CLI entry point
• retain detailed command, distribution, and conformance material under docs/
• remove retired docs-handoff automation and the asymmetric CLI/Python fixture workflow
• keep release builds, checksums, attestations, reproducibility, and public download verification intact

Validation

• 859 PHPUnit tests passed on Ubuntu as an unprivileged user
• 18 Node release-contract tests passed
• 8 native-prerequisite tests passed
• workflow YAML parsed successfully
• retained shell and Node scripts passed syntax checks
• changed Markdown local links validated
• public-boundary scan and git diff --check passed