[Code Quality] Add antigravity engine to docs/reference/engines.md and JSON schema

[github-actions]

Description

The antigravity engine is a fully supported built-in engine registered in the runtime (pkg/workflow/engine_definition.go:18, pkg/workflow/antigravity_engine.go:22) and is actively used in production workflows (.github/workflows/smoke-antigravity.md). However, it is missing from the documentation and JSON schema, causing it to appear unsupported or invalid to users.

Suggested Changes

1. Update docs/src/content/docs/reference/engines.md: Add antigravity to the available engine table alongside claude, codex, copilot, gemini, opencode, and pi
2. Update pkg/parser/schemas/main_workflow_schema.json: Add antigravity to the engine_config built-in engine description/examples so the schema matches the runtime catalog

Files Affected

• docs/src/content/docs/reference/engines.md (engine table at lines 14–21)
• pkg/parser/schemas/main_workflow_schema.json (engine_config definition)

Success Criteria

• engines.md lists antigravity in the available engines table
• main_workflow_schema.json includes antigravity in built-in engine descriptions/examples
• Runtime engine catalog and docs/schema are in sync
• Consider adding a regression test that diffs runtime engine IDs against docs/schema enumerations

Source

Extracted from Schema Consistency Check - 2026-07-15

Finding: antigravity registered in runtime but omitted from schema-facing built-in engine descriptions and engines.md table.

Priority

Medium — valid workflows using antigravity appear undiscoverable or invalid via schema/docs

🔍 Task mining by Discussion Task Miner - Code Quality Improvement Agent · 119.8 AIC · ⌖ 5.28 AIC · ⊞ 7K · ◷

• expires on Jul 16, 2026, 11:17 AM UTC-08:00

[github-actions]

This issue was automatically closed because it expired on 2026-07-16T19:17:07.835Z.

Closed by Workflow