Bug: Egyptian hieroglyphs

U+13000–1342F get the USE class HIEROGLYPH (18). In the KBTS_SHAPER_USE reorder pass (~line 23977), SawBase only counts BASE, BASE_OTHER and BASE_NUM. Every hieroglyph cluster therefore looks baseless, and the Scratchpad->RealCluster && !SawBase check (~line 24032) inserts U+25CC before each one. That also explains why refpad shows the same thing. Spaces are class OTHER, so they never form a cluster.

Try this one-line fix in the header:
SawBase |= KBTS__IN_SET64(Glyph->UseClass, KBTS__SET64((KBTS_USE_SYLLABIC_CLASS_BASE)
                                                     (KBTS_USE_SYLLABIC_CLASS_BASE_OTHER)
                                                     (KBTS_USE_SYLLABIC_CLASS_BASE_NUM)
                                                     (KBTS_USE_SYLLABIC_CLASS_HIEROGLYPH)));