PHLEGM v8 - SuperPET display startup qualification

Problem: the SuperPET-9000 hardware conformance selftest checks banked RAM and
CPU-selector features not yet supported by the native runtime.  The original
SELFTEST-QUICK invoked that full test, failed, and prevented MachineShowDisplay.
This was previously misread as a running SuperPET with a missing display.

Changes:
- startup_selftest_file opt-in descriptor key, used by SELFTEST-QUICK on fresh
  machine starts (not by full SELFTEST).
- SuperPET startup qualification checks loaded profile shape, mapped screen
  RAM, support-chip register responses, display bindings and keyboard mappings.
- The exhaustive selftest.config.phlegm is unchanged. It still fails loudly
  if banked RAM / CPU-selector functionality remains unimplemented.
- Console diagnostics announce display creation and startup test failures.
- No ROM binaries, Python, or changes to CPU-specific microcode are included.

Expected test:
With verified SuperPET ROMs and networking enabled, MACHINE commodore
SuperPET-9000 must report a successful startup qualification, cold boot, then
'Machine display opened: [0] Primary ...'.  Check the content of that display.
Full SELFTEST of SuperPET is NOT yet expected to pass; secondary CPU and its
bank mapping remain outstanding work.  This patch does not claim full SuperPET
emulation or performance validation.
