[Idea] add native hook adaptation support for Antigravity target

[bravest-cat]

What outcome do you need?

Summary

Currently, npx ecc-universal install --target antigravity maps rules (.agents/rules/), workflows (.agents/workflows/), skills (.agents/skills/), and agents (.agents/agents/). However, ECC's hook lifecycle (hooks/hooks.json / guardrails) is not adapted for Antigravity, relying solely on static rules/prompt constraints.

Antigravity natively supports an event-driven hook lifecycle engine. ECC should adapt and register equivalent hooks when running with --target antigravity.

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Context & Antigravity Hook Capabilities

Antigravity supports structured workspace lifecycle hooks categorized into:

• Inspect Hooks (read-only, async): Telemetry, audit trails, and execution observers (e.g., PostToolCallHook).
• Decide Hooks (blocking, gating): Permission validation and pre-execution safety filters (e.g., PreToolCallDecideHook, PreTurnHook).
• Transform Hooks (blocking, modifying): Intercepting errors or mutating inputs/outputs (e.g., OnToolErrorHook, OnInteractionHook).

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Proposed Behavior

1. Adapter Mapping:
   Update the installer script (in scripts/install.js and install.sh) to detect and translate compatible hooks from hooks/hooks.json (such as pre-commit validation, destructive command guards, or linter triggers) into Antigravity’s hook configuration schema.
2. Lifecycle Management:
   Include hook registrations in .agents/ecc-install-state.json so that doctor.js, repair.js, and uninstall.js track and clean them up alongside rules and skills.

What do you do today?

No response

Which harness is affected?

Another harness

What would success look like?

Impact

• Parity: Brings Antigravity users the same active guardrail and validation loop protections that Claude Code users get.
• Safety: Eliminates reliance purely on LLM adherence to markdown rules for critical pre-execution checks (e.g., preventing forbidden bash commands or accidental file overwrites).