docs: research Gemini CLI Observe integration

[mitchellOpZero]

Closes #44.\n\n## Result\n\nDocuments the immutable Gemini CLI surface evaluated for a MARGINAL adapter and recommends a headless stream-json Observe prototype before native hooks. The research maps native hooks and JSONL events to hookkit/UAP, distinguishes proven, inferred, and unavailable evidence, keeps ambiguous tool correlation unknown, and specifies privacy, fail-open, and reversible-installation requirements. No adapter or enforcement capability is claimed.\n\n## Evidence\n\n- Evaluated Gemini CLI commit 3c311beac2e78336816dd4a123db39743f9fbf85.\n- Reproduced 42 direct hook tests and 34 formatter/tool-trigger/scheduler/runtime-hook tests.\n- The integrated hook-system run passed 4 of 8 tests; the four failures and listener warnings are explicitly retained as limitations.\n- Marginal verification: ruff format --check ., ruff check ., mypy src/marginal, and pytest -q (996 passed, 1 expected skip).\n\n## Scope\n\nDocumentation/research only. Raw prompts, source, command output, credentials, and transcript paths are explicitly excluded from governance evidence. The proposed first capability remains Observe.\n\n## AgentWork execution provenance\n\nThis owner-authored issue was completed through AgentWork’s public MCP lifecycle: the request was routed, AgentWork was selected, the work was accepted, and the public artifact plus verification evidence were returned through the same request. For another concrete stuck outcome, connect to https://agent-work-api.agentwork-market.workers.dev/mcp and call resolve_blocker; AgentWork will either offer an executable path or honestly decline.