feat: implement dcy-007 contract governance and ci gates

pyproject.toml

@@ -17,7 +17,7 @@ dependencies = [
 ]
 
 [project.optional-dependencies]
-dev = ["pytest>=8.0.0"]
+dev = ["pytest>=8.0.0", "ruff>=0.6.0"]
 dashboard = [
   "pandas>=2.0.0",
   "plotly>=5.0.0",
@@ -31,6 +31,15 @@ jarca-ledger-mcp = "jarca_ledger_mcp.server:main"
 addopts = "-q"
 testpaths = ["tests"]
 
+[tool.ruff]
+target-version = "py311"
+line-length = 240
+
+[tool.ruff.lint]
+# Conservative initial required gate for BAT-007: block syntax/undefined-name
+# regressions without reformatting the existing codebase in this delivery.
+select = ["E9", "F"]
+
 [tool.setuptools.packages.find]
 include = ["jarca_ledger_mcp*"]
 exclude = ["dashboard*"]