fix(compile): compile only for the requested script context

fix(compile): compile only for the requested script context

Compiling for all three contexts let the narrowest one reject a policy
that is valid for the requested type: a 9-of-16 multisig, fine as
taproot multi_a, failed even for --type tr because legacy hit the
520-byte consensus limit on script elements.

The same policy also panicked for --type wsh,
which the test now covers.