A Blade reads the 65816's native-mode vectors from the RAM under the KERNAL
at $FFE4-$FFEF. native_vectors_init puts handlers' addresses there: IRQ and
NMI save A, X, and Y at full width, the direct page, and the data bank, push
the frame an emulation-mode interrupt makes, and run the KERNAL's handlers
through CINV and NMINV in 8-bit native mode, whose RTI comes back to restore
everything. BRK, COP, and ABORT go to the BRK handler, which on a Blade first
sets the direct page and data bank to 0 and returns to emulation mode.
