ssh-mcp v2 removed --password from the command line and reads
SSH_MCP_PASSWORD instead, so an old config crashes on startup. Add a
data-driven FLAG_ENV_MIGRATIONS registry plus detect_migratable_package,
migrate_removed_flags and removed_flag_warnings in bcc_core, and a
'Fix: move to environment variables' one-click action + warning in the
stdio server editor, with a matching main-window lint line. The literal
value lands in env{} (the only form Claude Desktop honours). 14 tests.