Gemini CLI adapter

[deanbot]

Context

Gemini CLI is used by developers who complement Claude usage with Google's model (different pricing tiers, different strengths). Gemini CLI has an extension system (gemini extensions install) that could provide native skill integration. Without a native adapter, the generic AGENTS.md fallback applies.

What "done" looks like

• adapters/gemini/ created with full executor and reviewer prompts in Gemini CLI's idiom
• Scheduling uses Gemini's native mechanism, or cron fallback documented
• adapters/gemini/install.sh added using gemini extensions install
• Root README.md adoption table updated
• Gemini adapter implements the full adapter contract from spec/SPEC.md
• Loop invariant implemented via native mechanism or documented as manual step
• Install is a single command

Notes / Open questions

• Gemini CLI extension schema and directory structure
• Whether Gemini CLI has a loop or scheduling primitive
• Whether Gemini CLI reads AGENTS.md natively