fix(isc): drop the broken compiled artifact — the DSL grammar is the engine

The shipped isc.artifact.json misparses lowercase system codes
(acadsin-zho-Hani-Latn-2002.isc) — and a FRESH compile with
parsanol 1.3.91 reproduces the identical failure, i.e. the parg
compiler mistranslates the grammar (filed upstream as parsanol#5).
The artifact path has never parsed this corpus correctly; the Ruby
DSL grammar is the only engine that has.

Per the clean-data rule, ship no known-bad derived bytes: the
.parg source stays (canonical grammar, used by the differential
spec once the compiler is fixed), the artifact spec guards skip
without it, and the runtime uses its documented artifact-missing
fallback into the Ruby grammar.

Author: ronaldtse