Add AI contribution policy guidance

[Rohithmatham12]

What this changes

• Adds contributor guidance for substantial AI-assisted issues, pull requests, and comments.
• Clarifies that contributors remain responsible for correctness, testing, licensing, security, and responding to review.
• Updates stale conformance/trademark language that referenced a 2021 task force deadline.

Fixes #1691.
Updates #1174.

Testing

• GOCACHE=/private/tmp/istio-community-go-cache GOMODCACHE=/private/tmp/istio-community-go-mod-cache go test ./...

[linux-foundation-easycla]

• ❌ - login: @Rohithmatham12 / name: Rohithmatham12. The commit (cca4d41) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please visit our EasyCLA portal and chat with our support bot.

[istio-testing]

Hi @Rohithmatham12. Thanks for your PR.

I'm waiting for a istio member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[Rohithmatham12]

Hi @istio/steering-committee, PTAL when you have a chance? This PR is waiting on code-owner review and /ok-to-test so the required community jobs can run.

One blocker remains on my side: @linux-foundation-easycla reports that CLA authorization is missing for commit cca4d41, so I will complete the EasyCLA authorization separately.

I verified locally with:

GOCACHE=/private/tmp/istio-community-go-cache GOMODCACHE=/private/tmp/istio-community-go-mod-cache go test ./...

Thanks!