feat(claude): add sub-agents, global instructions, and expand permissions

[Okabe-Junya]

Summary

• Add 10 specialized sub-agents for Claude Code (k8s-expert, go-pro, python-expert, ts-developer, shell-master, ci-cd-specialist, architect, code-reviewer, doc-reviewer, terraform-expert)
• Add global CLAUDE.md with Git workflow standards (branch naming with Okabe-Junya/ prefix, semantic commit messages)
• Expand and clean up allowed/ask permissions in settings.json (Go, Python, Node.js/TypeScript focused)
• Disable co-author attribution in commits/PRs
• Update symlink.zsh to link agents/ and CLAUDE.md to ~/.claude/

Test plan

• Run make symlink to verify symlinks are created correctly
• Verify ~/.claude/agents/ contains all sub-agents
• Verify ~/.claude/CLAUDE.md is linked correctly
• Verify ~/.claude/settings.json contains updated permissions