feat: ship agent team phase 1 MVP

[dongowu]

Summary

• add Phase 1 MVP product surfaces with agent and worker catalog APIs, governance approval gates, and engineering-ready templates/docs
• stabilize Windows acceptance and cross-platform runtime tests by removing the python dependency, normalizing request/path handling, and fixing shell-specific test assumptions
• document the agent-team rollout plan and integration playbook so the new capabilities are easier to adopt and extend

Verification

• go test ./...
• cargo test --manifest-path runtime/Cargo.toml
• ./scripts/acceptance.sh