Google Antigravity revives planning mode with /plan

This is a sensible rollback disguised as a refinement: developers clearly wanted control over when agents plan, while still keeping fast execution available.

• –`/plan` gives users an intentional boundary between analysis and code changes.
• –Reviewable implementation plans improve trust for multi-file and higher-risk work.
• –The change reflects strong user feedback, but repeated mode redesigns can erode confidence in Antigravity’s product direction.
• –Developers should reserve `/plan` for architectural work, unfamiliar codebases, and risky refactors; small fixes can stay on the fast path.
• –The feature is an incremental product update, not a fundamentally new capability.