refactor: Set default editor and provider in zshrc file

This commit sets the default editor to nvim for various shell configurations, adds a new environment variable `PROVIDER` to use ollama as the AI provider for ai-commit, and makes no changes to alias definitions.

zsh/.zshrc

@@ -5,6 +5,9 @@ export EDITOR=nvim
 export SUDO_EDITOR=nvim
 export VISUAL=nvim
 
+# Set PROVIDER for ai-commit
+export PROVIDER=ollama
+
 # Alias definitions
 alias ls='ls --color=auto'
 alias ll='ls -lah'