chore: nuke tests/ and the entire test toolchain

The test suite was carrying migration scars and a long tail of
low-density assertions over SDK-derived behavior. Drop it wholesale.

- Delete ``tests/`` (42 files, ~4900 LoC).
- Drop ``pytest`` / ``pytest-asyncio`` / ``pytest-cov`` /
  ``pytest-mock`` from the dev dependency group; ``uv sync``
  uninstalls the matching wheels.
- Strip the pytest + coverage config blocks, the
  ``flake8-pytest-style`` ruff selector, the ``tests/**`` per-file
  ignores, the ``[tool.mypy.overrides] tests.*`` block, and the
  ``"tests"`` entry from bandit's ``exclude_dirs``.
- Drop the ``test`` / ``test-cov`` Makefile targets; ``dev`` no
  longer depends on tests.
- Strip the ``# Testing`` block from ``.gitignore`` (``.coverage``,
  ``.pytest_cache/``, ``htmlcov/``, ``coverage.xml``, ``nosetests.xml``,
  ``.tox/``, ``.hypothesis/``).

ruff (27) and mypy (82) baselines unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Makefile

@@ -1,4 +1,4 @@
-.PHONY: help install dev-install format lint type-check test test-cov clean pre-commit setup-dev
+.PHONY: help install dev-install format lint type-check security check-all clean pre-commit setup-dev dev
 
 help:
 	@echo "Available commands:"
@@ -13,10 +13,6 @@ help:
 	@echo "  security      - Run security checks with bandit"
 	@echo "  check-all     - Run all code quality checks"
 	@echo ""
-	@echo "Testing:"
-	@echo "  test          - Run tests with pytest"
-	@echo "  test-cov      - Run tests with coverage reporting"
-	@echo ""
 	@echo "Development:"
 	@echo "  pre-commit    - Run pre-commit hooks on all files"
 	@echo "  clean         - Clean up cache files and artifacts"
@@ -59,17 +55,6 @@ security:
 check-all: format lint type-check security
 	@echo "✅ All code quality checks passed!"
 
-test:
-	@echo "🧪 Running tests..."
-	uv run pytest -v
-	@echo "✅ Tests complete!"
-
-test-cov:
-	@echo "🧪 Running tests with coverage..."
-	uv run pytest -v --cov=strix --cov-report=term-missing --cov-report=html
-	@echo "✅ Tests with coverage complete!"
-	@echo "📊 Coverage report generated in htmlcov/"
-
 pre-commit:
 	@echo "🔧 Running pre-commit hooks..."
 	uv run pre-commit run --all-files
@@ -78,13 +63,10 @@ pre-commit:
 clean:
 	@echo "🧹 Cleaning up cache files..."
 	find . -type d -name "__pycache__" -exec rm -rf {} + 2>/dev/null || true
-	find . -type d -name ".pytest_cache" -exec rm -rf {} + 2>/dev/null || true
 	find . -type d -name ".mypy_cache" -exec rm -rf {} + 2>/dev/null || true
 	find . -type d -name ".ruff_cache" -exec rm -rf {} + 2>/dev/null || true
-	find . -type d -name "htmlcov" -exec rm -rf {} + 2>/dev/null || true
 	find . -name "*.pyc" -delete 2>/dev/null || true
-	find . -name ".coverage" -delete 2>/dev/null || true
 	@echo "✅ Cleanup complete!"
 
-dev: format lint type-check test
+dev: format lint type-check
 	@echo "✅ Development cycle complete!"