Prepare Show HN launch

[ayhammouda]

Why

Show HN is useful only if the project is instantly understandable and installable. Launching there before PyPI works would waste the shot.

Blocked by

• PyPI package install works.
• README has a demo.
• At least one clean install/test path has been verified.

Acceptance criteria

• Draft a concise Show HN title and body.
• Include the problem, what makes it different, and one demo query.
• Verify the first-run path on a clean machine/environment before posting.
• Post only after launch blockers are closed.