Add HLE CD BIOS and CD boot test harness

jagcd_hle: high-level emulation of the CD BIOS jump table — extracts
boot stub, populates TOC, intercepts CD_read/CD_poll/CD_stop calls
to transfer sectors directly from disc image to RAM. Enables CD boot
without a real BIOS ROM.

test_cd_boot: headless test harness that loads a CUE/BIN via dlsym,
runs frames, and dumps 68K register state and RAM contents for
debugging the CD boot sequence.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: JoeMatt