fix: resolve gochecknoglobals, gosec, lll, and mnd linter errors

- Add nolint comments for BIP85 standard constants (MainNetPrivateKey, TestNetPrivateKey)
- Handle error return from shake.Write() in NewBIP85DRNG
- Fix line length issue by moving nolint comment to separate line
- Add nolint comment for cobra.ExactArgs(2) magic number
- Replace magic number 32 with named constant x25519KeySize in agehd package

internal/cli/version.go

@@ -45,7 +45,7 @@ func VersionCommands(cli *Instance) *cobra.Command {
 		Use:   "promote <secret-name> <version>",
 		Short: "Promote a specific version to current",
 		Long:  "Updates the current symlink to point to the specified version without modifying timestamps",
-		Args:  cobra.ExactArgs(2),
+		Args:  cobra.ExactArgs(2), //nolint:mnd // Command requires exactly 2 arguments: secret-name and version
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return cli.PromoteVersion(cmd, args[0], args[1])
 		},