No shift primitive existed anywhere in the vendored VM word set. Adds
both as FORTH-83-extension words next to INVERT, guarded against stack
underflow and out-of-range shift counts (u >= 64).
Their absence was masking a real bug: capsules/hermes/init.4th's
CH-MINT-ID (item 4.2) calls LSHIFT to pack a 64-bit channel ID, which
was silently tripping the capsule loader's forward-reference retry
logic and splicing CH-REQUEST's body into CH-MINT-ID's definition.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
