PHLEGM v8 / Checkpoint 57 - Complete opcode definition/classification audit

Goal: Every opcode *defined by a chipset's hardware/CFG instruction space* must
have exactly one classification (valid / undocumented / illegal) and an explicit
CFG implementation (or an intentional illegal-operation handler). A class flag
is not itself proof of electrically accurate instruction behavior.

Canonical inventories inspected from Checkpoint 56:

Chipset                            Valid    Undocumented    Illegal    Total
2A03/Ricoh-RP2A03                   151         93           12       256
6502/MOS-6502                      151         93           12       256
6502/MOS-6510                      151         93           12       256
5A22/Ricoh-5A22                    256          0            0       256
6809/Motorola-MC6809               268          0          498       766
8080/Intel-8080                    244         12            0       256
8080/Intel-8080A                   244         12            0       256
8080/Intel-8085                    246         10            0       256
z80/Zilog-Z80                      698        748            0      1446
z80/Zilog-Z80A                     698        748            0      1446
S-SMP/SPC700                        256          0            0       256

Additional nonhardware sample CFG processors:
imaginary/Brainfuck-CPU             256          0            0       256
imaginary/Example-NOVA8              5          0            0         5
(The NOVA8 sample defines five instructions intentionally; its other byte
values do not belong to the sample's declared opcode namespace.)

Processor-specific namespace interpretation:
- 6502, 6510, 2A03, 5A22, 8080, 8080A, 8085, SPC700: each of the 256
  one-byte opcode values must be defined exactly once.
- 6809: primary page has 254 slots excluding prefix bytes $10 and $11.
  Each secondary page $10xx and $11xx has 256 classified slots: 766 total.
  Undefined MC6809 slots are deliberately declared illegal; actual behavior
  for all illegal silicon encodings has NOT been established.
- Z80/Z80A: 252 non-prefix unprefixed opcodes, full CB and ED pages (256
  each), full indexed CB pages DDCB**xx and FDCB**xx (256 each), 85 explicit
  IX opcodes, 85 explicit IY opcodes: 1446 classified instructions.
  A DD/FD prefix that does not alter a following instruction is consumed by
  the data-driven decoder's last-prefix-wins/ignored-prefix behavior; it does
  not create an additional distinct opcode definition. Arbitrarily repeated
  index prefixes likewise do not constitute missing opcode entries.
- SPC700: all 256 documented encodings are valid. No illegal/undocumented
  opcode class is claimed for this particular processor. Undocumented S-SMP
  hardware registers are separate from instruction opcode classification.

Changes made:
1) src/lib/spc700-support.bi now retains the per-opcode classification and
   insists on valid=256, undocumented=0, illegal=0 before accepting its
   runtime-compiled CFG. It also rejects any valid SPC700 entry implemented
   using the unsupported placeholder TRAP primitive.
2) tools/Validate-Opcode-Definitions.ps1 performs a standalone exhaustive
   audit of all primary opcode files, classifications, cycles, duplicate keys,
   paired mnemonic indexes, and the processor-specific opcode namespace.
   Run on Windows from PHLEGM v8:
     powershell -NoProfile -ExecutionPolicy Bypass -File tools/Validate-Opcode-Definitions.ps1
   This audit script does not modify any CFG files or require Python.
3) No opcodes were reclassified solely to make count checks pass, no
   undocumented opcode was replaced with NOP, and no CPU-specific opcode
   behavior was moved into microcode.lib.

Scope limits:
- This checks *definition coverage and classification consistency*; it is NOT
  an exhaustive hardware-conformance test of result values, cycles, buses,
  Z80 redundant-prefix timing, unstable NMOS unofficial behavior, MC6809
  illegal silicon behavior or SPC700 timing/peripherals.
- Native PowerShell / FreeBASIC execution must be confirmed on a machine with
  those runtimes installed. This checkpoint was additionally examined by a
  private platform-independent audit, which is not part of the distribution.
