test: add integration tests for all modules

- Add pytest-asyncio dev dependency and configure asyncio_mode=auto
- Add filterwarnings to suppress third-party PydanticDeprecatedSince20
- Add conftest.py with shared fixtures (project_dir, write_config, etc.)
- Add test_config.py: YAML loading, target type inference, model resolution
- Add test_graph.py: DAG construction, cycle detection, build ordering
- Add test_state.py: hash functions, state persistence, dirty checking
- Add test_builder.py: full build pipeline with FakeProvider, incremental
  builds, selective builds, error isolation, dependency cascading
- Add test_providers.py: ImageProvider and TextProvider with mocked clients
- Add test_cli.py: build/clean/graph commands via typer CliRunner
- All 94 tests pass with 0 basedpyright warnings

uv.lock

@@ -75,6 +75,7 @@ dependencies = [
 dev = [
     { name = "basedpyright" },
     { name = "pytest" },
+    { name = "pytest-asyncio" },
     { name = "ruff" },
 ]
 
@@ -92,6 +93,7 @@ requires-dist = [
 dev = [
     { name = "basedpyright", specifier = ">=1.38.0" },
     { name = "pytest", specifier = ">=9.0.2" },
+    { name = "pytest-asyncio", specifier = ">=0.25.0" },
     { name = "ruff", specifier = ">=0.15.1" },
 ]
 
@@ -557,6 +559,18 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/3b/ab/b3226f0bd7cdcf710fbede2b3548584366da3b19b5021e74f5bde2a8fa3f/pytest-9.0.2-py3-none-any.whl", hash = "sha256:711ffd45bf766d5264d487b917733b453d917afd2b0ad65223959f59089f875b", size = 374801, upload-time = "2025-12-06T21:30:49.154Z" },
 ]
 
+[[package]]
+name = "pytest-asyncio"
+version = "1.3.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pytest" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/90/2c/8af215c0f776415f3590cac4f9086ccefd6fd463befeae41cd4d3f193e5a/pytest_asyncio-1.3.0.tar.gz", hash = "sha256:d7f52f36d231b80ee124cd216ffb19369aa168fc10095013c6b014a34d3ee9e5", size = 50087, upload-time = "2025-11-10T16:07:47.256Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/e5/35/f8b19922b6a25bc0880171a2f1a003eaeb93657475193ab516fd87cac9da/pytest_asyncio-1.3.0-py3-none-any.whl", hash = "sha256:611e26147c7f77640e6d0a92a38ed17c3e9848063698d5c93d5aa7aa11cebff5", size = 15075, upload-time = "2025-11-10T16:07:45.537Z" },
+]
+
 [[package]]
 name = "python-dateutil"
 version = "2.9.0.post0"