feat: move the terminal fully into the ssh-terminal plugin (B9)

drizzle/postgres/0039_violet_firedrake.sql

@@ -0,0 +1,5 @@
+-- command_history moved to the ssh-terminal plugin, whose first migration
+-- renames it to p_ssh_terminal_command_history. Dropping it here would lose
+-- every saved command, so this only stops drizzle tracking it. SELECT 1
+-- because MySQL rejects an empty query.
+SELECT 1;