Harden npm alpha readiness for npx installs

[slashdevcorpse]

Scope

Prepare CodexClaw for the first public npm alpha so the intended npx workflow is clear and verifiable.

Acceptance Criteria

• README and package README explain the alpha npx path without claiming a publish before it exists.
• Package metadata includes public npm fields for repository, bugs, homepage, keywords, and alpha publish config.
• Release command publishes with the alpha dist-tag.
• Local CLI examples match commands that work from a source checkout.
• Package dry run and npm publish dry run show the expected alpha package contents.

Notes

This complements #13. Issue #13 remains the actual first-publish tracker unless the npm account is authenticated and the publish succeeds.