docs: clarify shellenv should be added at end of config file

Revert the compdef check and instead document that users should
add 'source <(wt shellenv)' at the END of their ~/.zshrc or ~/.bashrc,
after compinit (for zsh users).

This is simpler and follows the standard pattern used by other CLI tools.
The compdef error will be avoided by proper placement in the config file.

Changes:
- Update shellenv help text to emphasize END of config file
- Add note for zsh users to place after compinit
- Update README with same instructions
- Revert compdef existence check (no longer needed)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: timvw

README.md

@@ -53,14 +53,16 @@ sudo cp bin/wt /usr/local/bin/
 
 ### Shell Integration (Optional but Recommended)
 
-Add this to your `~/.bashrc` or `~/.zshrc`:
+Add this to the **END** of your `~/.bashrc` or `~/.zshrc`:
 
 ```bash
 source <(wt shellenv)
 ```
 
+**Note for zsh users:** Place this after `compinit` in your config file.
+
 This enables:
-- Automatic `cd` to worktree after `checkout`/`create`/`pr` commands
+- Automatic `cd` to worktree after `checkout`/`create`/`pr`/`mr` commands
 - Tab completion for commands and branch names
 
 ## Usage

main.go

@@ -400,11 +400,13 @@ var shellenvCmd = &cobra.Command{
 	Short: "Output shell function for auto-cd (source this)",
 	Long: `Output shell integration code for automatic directory navigation.
 
-Add this to your ~/.bashrc or ~/.zshrc:
+Add this to the END of your ~/.bashrc or ~/.zshrc:
   source <(wt shellenv)
 
+Note: For zsh, place this AFTER compinit to enable tab completion.
+
 This enables:
-- Automatic cd to worktree after checkout/create/pr commands
+- Automatic cd to worktree after checkout/create/pr/mr commands
 - Tab completion for commands and branch names`,
 	Run: func(cmd *cobra.Command, args []string) {
 		fmt.Print(`wt() {
@@ -477,10 +479,7 @@ if [ -n "$ZSH_VERSION" ]; then
             esac
         fi
     }
-    # Only set up completion if compdef is available (after compinit)
-    if (( $+functions[compdef] )); then
-        compdef _wt_complete_zsh wt
-    fi
+    compdef _wt_complete_zsh wt
 fi
 `)
 	},