fix: use correct hooks.json format with event names as object keys

[matanryngler]

Summary

• Fixes hooks.json to use the correct plugin hooks format (event names as object keys) instead of the array-with-event-field format
• The previous format caused hooks to silently not register, meaning DeployShield's PreToolUse guard and SessionStart context were never triggered

Test plan

• Verified validate-cloud-command.py correctly blocks kubectl apply when invoked directly
• Restarted Claude Code session and confirmed kubectl apply is now blocked by the hook