[deep-report] [quick-win] Document the antigravity engine in engines.md

[github-actions]

Description

The antigravity engine is implemented (pkg/workflow/antigravity_engine.go) and in active use (.github/workflows/smoke-antigravity.md sets engine.id: antigravity), but it is not documented in docs/src/content/docs/reference/engines.md (verified: 0 mentions). The engine list there shows Copilot, Claude, Codex, Gemini, Crush, OpenCode, and Pi — understating the supported engine set and causing false negatives for users and tooling.

Fix

Add an Antigravity section to engines.md and include antigravity in the schema engine description/example lists in main_workflow_schema.json $defs.engine_config.

Expected Impact

Generated docs and schema guidance reflect the real supported engine set.

Suggested Agent

Developer Documentation / Copilot SWE Agent.

Estimated Effort

Fast (< 30 min)

Data Source

DeepReport 2026-06-29; Schema Consistency Check #42193 (verified on main).

Generated by 🔬 DeepReport - Intelligence Gathering Agent · 212.1 AIC · ⌖ 11.9 AIC · ⊞ 9.8K · ◷

• expires on Jul 1, 2026, 8:05 AM UTC-08:00

[github-actions]

🍪 Issue Monster selected this for Copilot

I've identified this issue as a good candidate for automated resolution and requested assignment to the Copilot coding agent.

If assignment succeeds, the Copilot coding agent will analyze the issue and create a pull request with the fix.

Om nom nom! 🍪

🍪 Om nom nom by Issue Monster · 3.35 AIC · ⌖ 36.1 AIC · ⊞ 7.7K · ◷