Scaffold CMOS 18 reformatter: harness, linter, parser, formatter, CLI

Initial phase-1 baseline of the karpathy/autoresearch-style loop.
The formatter module is the inner-loop artifact; parser and linter
are infra. The linter carries a LINTER_VERSION hash (v0.2.0) that
will force a re-baseline on any rule change.

Components:
- harness/diff.py: case-sensitive field-level substring diff
- harness/score.py: three-axis scoring (field, linter, canary exact)
- src/cmos/linter.py: 9 CMOS 18 structural rules, each Purdue/CMOS cited
- src/cmos/parser.py: locate ## Bibliography section, split entries
- src/cmos/formatter.py: prompt + OpenAI call with caller injection
- src/cmos/cli.py: cmos format path/to/draft.md
- scripts/run_loop.py: loop runner with --fake mode for no-API runs
- exemplars/: 3 canary seed exemplars (book, journal w/DOI, web),
  sourced from chicagomanualofstyle.org quick guide

Tests: 48 passing. Fake-mode baseline scalar = 0.000 on the 3 seed
exemplars (identity caller fails the linter on every rule). This is
the floor the real GPT-5 formatter needs to improve from.

pyproject.toml

@@ -0,0 +1,34 @@
+[project]
+name = "cmos"
+version = "0.1.0"
+description = "Reformat arbitrary English-language drafts to Chicago Manual of Style 18th edition (notes and bibliography)."
+requires-python = ">=3.11"
+dependencies = [
+    "openai>=1.50.0",
+    "python-dotenv>=1.0.0",
+]
+
+[project.scripts]
+cmos = "cmos.cli:main"
+
+[dependency-groups]
+dev = [
+    "pytest>=8.0",
+    "black>=24.0",
+]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/cmos"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+addopts = "-v --tb=short"
+pythonpath = ["src", "."]
+
+[tool.black]
+line-length = 100
+target-version = ["py311"]