docs: bootstrap Trunk git-hooks in cloud agent environments

[yu-iskw]

Motivation

• Reduce CI failures caused by cloud/ephemeral coding agents by ensuring they run the same Trunk pre-commit and pre-push checks locally before commits/pushes.

Description

• Add a brief bootstrap note to AGENTS.md instructing cloud coding agents to run pnpm exec trunk git-hooks install once per checkout (and to repeat in disposable workspaces), and mirror the guidance in CLAUDE.md so the digest stays aligned with the canonical policy.

Testing

• Ran pnpm test (Vitest all green), pnpm lint:report (ESLint score 100), pnpm build (workspace build succeeded), pnpm knip (succeeded after build), and pnpm coverage:report (coverage report written), while pnpm lint failed in this environment because pnpm exec trunk check -y could not reach Trunk upstream (ENETUNREACH).

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Codex Task