PHLEGM v8 - checkpoint 42 - PET/CBM 2000/3000/4000 machine expansion

Source: checkpoint 41 Developer Distribution CoreDump-Name-41.
Scope: Commodore PET/CBM machine definitions only; no native build source or bootstraps modified.

New data-driven profiles (7):
  PET-2001-8B            : BASIC 2, business keyboard, 40x25 TTL, no CRTC; revised PET board; not original chiclet-keyboard Japanese 8B variant.
  PET-2001-16B           : BASIC 2, business keyboard, 40x25 TTL, no CRTC.
  PET-2001-32B           : BASIC 2, business keyboard, 40x25 TTL, no CRTC.
  CBM-3016B              : European CBM 3016B, BASIC 2, business keyboard, 40x25 TTL, no CRTC.
  PET-2001-32N-BASIC4    : PET 2001-32N with later BASIC 4.0 upgrade, normal/graphics keyboard, 40x25 TTL (pre-CRTC editor ROM 901447-29).
  PET-2001NT             : Teacher's PET 2001NT, 32 KiB normal/graphics-keyboard BASIC 4 configuration; 40x25 TTL, no CRTC. Actual Teacher edition ROM revision may differ.
  CBM-4004-N             : CBM 4004 nominal 4 KiB, BASIC 4.0, normal/graphics keyboard, 40x25 TTL (pre-CRTC 9-inch board).


Implementation:
  - Per-model machine.config.phlegm (CPU, RAM size, video, keyboard, memory mapping)
  - Per-model support-chips.config.phlegm (6502 system 6520/6522 mapping)
  - Per-model selftest.config.phlegm (RAM, PIA, VIA and firmware expectations)
  - Per-model firmware.config.phlegm (external URL and size/CRC-verified ROM slots)
  - Per-model keyboard.config.phlegm (original PET normal/business matrix)
  - No ROM data shipped. Runtime networking fetches/cache-verifies the declared firmware.
  - Reused existing 6502+PET generic emulation code; no CPU-specific logic hard-coded.
  - Existing PET-2001-32N retains BASIC 2; additional -BASIC4 profile explicitly selects upgrade ROMs.

Limitations:
  - This adds machine profiles, not proof of full-speed/accurate emulation.
  - Model hardware variations (CRT phosphor, cassette transport, board revisions) are not differentiated.
  - The nominal 2001-8B refers to the revised business-keyboard board; rare Japanese 8B
    chiclet-keyboard revision is not modeled separately.
  - PET-2001NT is modeled as a 32 KiB BASIC 4 normal/graphics-keyboard equivalent; historical
    Teacher edition and ROM revision variants are not exhaustively verified.
  - More distant families (VIC-20, C64, 264/+4, C128, CBM-II, Amiga) require new chipsets,
    graphics/sound/memory maps and will not function correctly by copying these profiles.
  - ROM boot/real video validation and native FreeBASIC --selftest-all still required.

Sources for historical model/ROM families:
  https://www.zimmers.net/cbmpics/cbm/PETx/petfaq.html
  https://www.zimmers.net/commie/canonical.php?cat=PET+2000+Series&prod=1
  https://groups.google.com/g/comp.sys.cbm/c/l92EwIqen04/m/kkD3jxGmCNYJ

Suggested manual test:
  PHLEGM --selftest-all (if supported by the target build)
  Load each model with Networking enabled, check BASIC prompt, RAM size and keyboard.
  Toggle PET video/character banks and inspect 40x25 output.
