Sprint 13: integrate gr2 team-workspace foundation

[laynepenney]

Summary

• integrate the Sprint 13 gr2 foundation from sprint-13 into main
• ship the new clean-break CLI entrypoint and internal crate split
• ship the initial team-workspace registry lifecycle for agents and repos

Includes

• #491 bootstrap gr2 binary
• #493 internal gr2 crate split
• #495 gr2 init
• #497 gr2 team add
• #499 gr2 team list
• #501 gr2 team remove
• #503 gr2 repo add
• #505 gr2 repo list
• #507 gr2 repo remove
• #508 sprint-branch integration of the repo lifecycle frontier

Verification

• cargo fmt --all --check
• cargo test --test cli_tests test_gr2_help -- --nocapture
• cargo test --test cli_tests test_gr2_doctor -- --nocapture
• cargo test --test cli_tests test_gr2_init_scaffolds_team_workspace -- --nocapture
• cargo test --test cli_tests test_gr2_team_add_registers_agent_workspace -- --nocapture
• cargo test --test cli_tests test_gr2_team_list_shows_registered_agents -- --nocapture
• cargo test --test cli_tests test_gr2_team_remove_deletes_registered_agent -- --nocapture
• cargo test --test cli_tests test_gr2_repo_add_registers_repo -- --nocapture
• cargo test --test cli_tests test_gr2_repo_list_shows_registered_repos -- --nocapture
• cargo test --test cli_tests test_gr2_repo_remove_deletes_registered_repo -- --nocapture