fix: ZDOTDIR and XDG_CONFIG_HOME config detecting (#51)

From this discussion:

https://www.reddit.com/r/zsh/comments/1v8rq7s/comment/p09b05o/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

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Problem: Iris hardcodes config paths to `~/.zshrc` and
`~/.config/fish/config.fish`. This ignores users' custom `ZDOTDIR` or
`XDG_CONFIG_HOME` setups, polluting their `$HOME` directory during init
and failing to scan their actual aliases. Also, ZDOTDIR is often set in
`~/.zshenv` without export, making it invisible to Go's `os.Getenv`

Solution:
- Bash: default `$HOME/.bashrc` so dont mind about it
- For Zsh, Iris now probes zsh directly (`zsh -c "echo $ZDOTDIR"`) with
a timeout to accurately resolve custom paths even if they aint exported
- For Fish, Iris now natively respects the `XDG_CONFIG_HOME` environment
variable
- Shared this robust resolution logic across init, uninstall, and alias
scanning
- Fixed alias scanning to process files in the correct zsh startup order
(`.zshenv` -> `.zprofile` -> `.zshrc`) and correctly merge them

root/init.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"github.com/spf13/cobra"
+	"github.com/versenilvis/iris/integration/shell"
 	"github.com/versenilvis/iris/internal/config"
 )
 
@@ -135,13 +136,13 @@ var setupCmd = &cobra.Command{
 
 		switch shellName {
 		case "zsh":
-			configFile = filepath.Join(home, ".zshrc")
+			configFile = filepath.Join(shell.GetZshConfigDir(), ".zshrc")
 			evalCmd = `eval "$(iris init zsh)"`
 		case "bash":
 			configFile = filepath.Join(home, ".bashrc")
 			evalCmd = `eval "$(iris init bash)"`
 		case "fish":
-			configFile = filepath.Join(home, ".config", "fish", "config.fish")
+			configFile = filepath.Join(shell.GetFishConfigDir(), "config.fish")
 			evalCmd = `iris init fish | source`
 		default:
 			fmt.Printf("Unsupported shell: %s. Please add iris init manually.\n", shellName)