build: migrate to buf v2

[miparnisari]

Description

Ran buf config migrate and buf def update and buf generate

References

• https://buf.build/docs/migration-guides/migrate-v2-config-files#how-to-migrate-to-a-v2-configuration

[curfew-marathon]

This PR has had no human activity for 90 days, so it has been marked lifecycle/stale.

This is automated backlog grooming, not a judgment on the work.

What happens next, unless there is activity:

• In 30 days, it will move to lifecycle/closing-soon
• 30 days after that, it will be closed

To keep it open, push a commit or leave a comment, and the clock will reset. For work that should not auto-close, such as an RFC or long-running experiment, ask a maintainer to add lifecycle/frozen.

[curfew-marathon]

This PR has had no human activity for 30 days since being marked lifecycle/stale, so it has now been marked lifecycle/closing-soon.

It will be closed in 30 days unless there is new activity.

If the work still matters, this is the moment to say so: leave a comment, push a commit, or ask a maintainer to add lifecycle/frozen if it should be kept open long-term.

If this work is no longer being pursued, no action is needed.