feat(zsh): add gcai AI commit message helper and cl alias

[nielsonm]

Summary

Adds two quality-of-life improvements to .zshrc:

gcai function

AI-powered commit message generator using agy. Generates a Conventional Commits 1.0.0 compliant message from staged changes with interactive confirm/edit/abort workflow.

cl alias

Shorthand for clear.

Changes

• Add gcai() function that:
  • Detects the git repo root via git rev-parse
  • Captures staged diff and embeds it in the agy prompt
  • Enforces Conventional Commits format (type, optional scope, description)
  • Offers [y]es / [e]dit / [n]o confirmation before committing
• Add alias cl='clear'