docs: add more help info to migrate cmd

crates/bin/pcli/src/command/migrate.rs

@@ -10,9 +10,12 @@ use termion::input::TermRead;
 
 #[derive(Debug, clap::Parser)]
 pub enum MigrateCmd {
-    /// Migrate your entire balance.
+    /// Migrate your entire balance to another wallet.
     ///
-    /// This will require a full viewing key over the command line as well.
+    /// All assets from all accounts in the source wallet will be sent to the destination wallet.
+    /// A FullViewingKey must be provided for the destination wallet.
+    /// All funds will be deposited in the account 0 of the destination wallet,
+    /// minus any gas prices for the migration transaction.
     #[clap(name = "balance")]
     Balance,
 }