Add hello-world JSON artifact

[go165]

Closes #36.

Summary:

• Add hello-world.json at the repository root with the exact requested JSON payload.

Validation:

• Parsed hello-world.json with Node.js and verified action=hello and object=world.
• Ran git diff --check.

Payout address if reward-eligible:

• 0x1f0130669ca6fd02e025a984cc038f139df19a2f

[go165]

Ready for review. This PR adds the exact root hello-world.json requested in #36 and closes the issue. I verified the JSON parses and matches { "action": "hello", "object": "world" }, and git diff --check is clean.