Define universal runner v1 protobuf contract + proto layout; add BSR publish workflow

[rowan-stein]

This updates the initial repo scaffolding to match the intended universal runner contract.

• Renames/generalizes from docker-specific naming to RunnerService (agynio.api.runner.v1).
• Switches proto layout to proto/<name>/<version>.
• Replaces placeholder with a real streaming exec + cancel contract.
• Adds CI workflow to publish to BSR on merges to main (requires BUF_TOKEN secret).

After merge:

• Configure BUF_TOKEN in repo secrets.
• Verify module publish to buf.build/agynio/api.

[github-actions]

The latest Buf updates on your PR. Results from workflow buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	⏩ skipped	Feb 23, 2026, 9:35 PM