feat(challenges): add AI coding-agent transcript challenge

[kekubhai]

What kind of changes does this PR include?

• Fixes or refactors
• A new challenge
• Additional documentation
• Something else

Description

Adds Challenge 71 for the AI category, demonstrating how sensitive information can persist inside an AI coding-agent session transcript.

The transcript was generated from a genuine OpenAI Codex CLI session during a debugging task involving a fake staging deployment token. The captured transcript contains realistic session metadata, commands, tool calls, outputs, errors, and agent reasoning.

The challenge requires finding the leaked secret from the persistent agent transcript rather than directly from the original .env file.

Also updates the challenge category configuration from ai_other_tech to ai and adds the Challenge 71 configuration and tests.

Relations

Closes #2657

References

The transcript was generated using OpenAI Codex CLI and preserved as the captured session artifact rather than being manually authored.

Checklist:

• All the contributions made are solely the work of me and my co-authors
• I used AI to generate parts of the content.
• I tested the changes in this PR (if applicable)
• I added unit tests to ensure my change works (when change in Java or on front-end code)
• I added UI tests to ensure my UI changes work (when change in the overall UI, not needed if just adding a challenge)
• The PR passes pre-commit hooks and automated tests

[commjoen]

Suggested change

	difficulty: *normal
	difficulty: *easy

[commjoen]

Hi @kekubhai ! thank you for another challenge! Can you please:

• rename the challenge to 72, as 71 is assigned to feat(docker): introduce Java 26 dev/build container and build-secret challenge 71 #2650
• fix the failing actions
  and then i can have another go over the files (probably next week)