Avoid Gemini loading Claude hook events

[Sonai124]

Fixes #137.

Summary

• Move the Claude/Codex hook map from Gemini's auto-discovered hooks/hooks.json path to hooks/claude-codex-hooks.json.
• Point both .claude-plugin/plugin.json and .codex-plugin/plugin.json at that host-specific hook config so SessionStart and UserPromptSubmit behavior remains available there.
• Add a Gemini regression test that prevents reintroducing root hooks/hooks.json, plus a manifest test for the shared hook path.
• Document why the Gemini adapter does not ship a root hook config.

Verification

• node scripts/check-rule-copies.js
• npm test (run with a temporary local python/python3 shim delegating to uv run --with pandas python, because this Windows shell has no Python on PATH)

Notes

Gemini CLI hard-codes extension hook discovery to hooks/hooks.json and does not define UserPromptSubmit; keeping Ponytail's Claude/Codex hook map out of that path avoids the invalid hook event warning.