Add boxsim CLI: pure Python codec, netlist extraction, KiCad project generation

Replaces the bpj2ini.py prototype with a packaged tool. The A2F codec is now
reimplemented in Python, so neither Boxsim.exe nor a CPU emulator is needed to
decode a container; the emulator survives as a development-only oracle that the
codec is differentially tested against.

Verified:
- 134 containers decode byte-identically to Boxsim's own decoder, 270 pre-2.0
  files rejected by both implementations (tools/difftest.py --self-test)
- Default.BPJ: 22 components, 14 nets, no dangling terminal
- 22 of 22 parts resolve to library symbols; one series inferred from a
  sibling, two DC resistance deviations reported
- ERC clean and the netlist KiCad extracts from the generated sheet is an
  identical partition to the one derived from the Boxsim grid
- container build byte-identical to the host build
- 32 tests passing, ruff clean

Decode time went 69 s -> 14.5 s (binding emulator hooks to trap addresses)
-> 1.6 s (pure Python).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pyproject.toml

@@ -0,0 +1,41 @@
+[build-system]
+requires = ["setuptools>=68"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "boxsim"
+version = "0.1.0"
+description = "Read Boxsim loudspeaker projects and generate KiCad projects from their crossovers"
+readme = "README.md"
+requires-python = ">=3.11"
+license = { text = "MIT" }
+authors = [{ name = "Marco Grätsch", email = "magdev3.0@gmail.com" }]
+keywords = ["boxsim", "visaton", "kicad", "loudspeaker", "crossover"]
+dependencies = []
+
+[project.optional-dependencies]
+# Development only: the reference decoder emulates Boxsim.exe to differentially
+# test the pure Python codec. Not needed to use the tool.
+oracle = ["unicorn>=2.0", "pefile>=2023.2.7"]
+dev = ["pytest>=8", "ruff>=0.6"]
+
+[project.scripts]
+boxsim = "boxsim.cli:main"
+
+[tool.setuptools]
+packages = ["boxsim"]
+
+[tool.setuptools.package-data]
+boxsim = ["data/*"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+addopts = "-q"
+
+[tool.ruff]
+line-length = 96
+target-version = "py311"
+
+[tool.ruff.lint]
+select = ["E", "F", "W", "I", "UP", "B", "C4", "SIM"]
+ignore = ["E501"]