Fix git hooks for Ava user

Git hooks (pre-push, post-merge, post-checkout, pre-commit) fail for Ava user due to:

• Missing CODEROOT environment variable
• Commands not in PATH (gitlint, etc)
• Assumptions about Ben's environment

Options: 1. Make hooks load direnv at the start 2. Use --no-verify consistently for Ava 3. Create Ava-specific hook overrides 4. Make hooks more defensive about missing env