F420 static and structural checks

build LLVM 18 SymCC: PASS
build LLVM 17 SymCC: PASS
py_compile changed Python modules: PASS
ruff check changed Python modules: PASS
technology index update/check: PASS
JSON and JUnit XML parse: PASS
diagram render and visual inspection: PASS
diagram PNG dimensions: 2400x1500
focused fixture files: 3
focused RUN commands: 28 (15 default/generated, 3 big-endian, 10 fallback)
v10 schema references in producer/strict consumer/checker: 33
F420 LLVM17 focused: 3/3 PASS
F420 LLVM18 focused: 3/3 PASS
F416--F420 LLVM17 related: 12/12 PASS
F416--F420 LLVM18 related: 12/12 PASS
F420 Python targeted: 6/6 PASS
F416--F420 Python related: 27/27 PASS
full Python gate: 1103 tests + 250 subtests PASS
full LLVM17 controlled gate: 296 PASS + 2 existing UNSUPPORTED