Align coverage gate with coverage.py multiprocessing support

.gitignore

@@ -27,4 +27,5 @@ ser/models/*.json
 .hypothesis
 .local/
 .coverage
-coverage.xml
+.coverage.*
+coverage.xml

CONTRIBUTING.md

@@ -31,6 +31,7 @@ make fmt       # pyupgrade --py312-plus + ruff --fix + isort + black
 make lint      # ruff + black --check + isort --check-only
 make type      # mypy + pyright (pythonversion 3.12)
 make test      # pytest -q
+make test-cov  # coverage.py branch gate, including multiprocessing workers
 make prepush-check      # canonical pre-push hook command
 make prepush-hook       # hook workflow: autofix + verify + abort if files changed
 make import-lint        # API boundary import lint lane (TID251 banned-api policy)

Makefile

@@ -49,7 +49,11 @@ test:
 	uv run pytest -q
 
 test-cov:
-	uv run --frozen --extra dev pytest -q --cov=ser --cov-report=term-missing --cov-report=xml
+	uv run --frozen --extra dev coverage erase
+	uv run --frozen --extra dev coverage run -m pytest -q
+	uv run --frozen --extra dev coverage combine
+	uv run --frozen --extra dev coverage report
+	uv run --frozen --extra dev coverage xml
 
 check: lint type test
 
@@ -79,3 +83,4 @@ quality-gate-full:
 clean:
 	find . -type d -name "__pycache__" -prune -exec rm -rf {} +
 	rm -rf .pytest_cache .mypy_cache .ruff_cache dist build .pkg-smoke
+	find . -maxdepth 1 -type f \( -name ".coverage" -o -name ".coverage.*" -o -name "coverage.xml" \) -delete

pyproject.toml

@@ -53,7 +53,6 @@ dependencies = [
 dev = [
   "pre-commit>=4.0.0,<5.0.0",
   "pytest>=8.0.0,<9.0.0",
-  "pytest-cov>=6.0.0,<7.0.0",
   "coverage[toml]>=7.6.0,<8.0.0",
   "hypothesis>=6.130.0,<7.0.0",
   "ruff>=0.9.0,<1.0.0",
@@ -184,7 +183,10 @@ reportMissingTypeStubs = "none"
 
 [tool.coverage.run]
 branch = true
+concurrency = ["multiprocessing"]
+parallel = true
 relative_files = true
+sigterm = true
 source = ["ser"]
 
 [tool.coverage.report]