docs: add CLAUDE.md guidance for AI assistants

[seonghobae]

Summary

Adds a CLAUDE.md at the repo root that points to AGENTS.md as the canonical agent guide (Security Scan gate, secrets-via-Env rule) and complements it with:

• Commands: wrangler dev/deploy, vitest including single-test invocation, typecheck, security scan, release:verify, and the KPI/readiness audit tooling. Notes explicitly that no lint script exists in package.json rather than inventing one.
• Architecture: the single-file Cloudflare Worker (src/index.ts) with its /health and /exchange routes, the OIDC-to-installation-token exchange flow, the contract-tested response envelope and headers, the structured http_request log schema feeding the KPI pipeline, in-isolate caches, and wrangler.toml vars/secrets (no KV/D1/queue bindings).
• Conventions: Unreleased-section changelog updates, mixed Korean/English docs, fail-closed posture.

🤖 Generated with Claude Code

https://claude.ai/code/session_019zWjgFjCupJNvARzcFETtR

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[Copilot]

Pull request overview

Adds a new CLAUDE.md document to guide Claude Code usage in this repo, explicitly deferring to AGENTS.md as the canonical cross-agent guardrail source (Security Scan gate expectations and secrets-via-Worker-Env rule).

Changes:

• Introduces CLAUDE.md with required-first-read guidance pointing to AGENTS.md.
• Documents the repo’s core commands (dev/deploy/test/typecheck/security/release verification) and CI/CD entry points.
• Summarizes the Worker’s architecture/contracts (/health, /exchange, response envelope/headers, logging schema, in-isolate caches, bindings).

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