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

tests/test_graph.py

@@ -0,0 +1,194 @@
+"""Integration tests for bulkgen.graph."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+from bulkgen.config import ProjectConfig
+from bulkgen.graph import build_graph, get_build_order, get_subgraph_for_target
+from tests.conftest import WriteConfig
+
+
+class TestBuildGraph:
+    """Test dependency graph construction from real configs."""
+
+    def test_single_target_no_deps(
+        self, project_dir: Path, simple_text_config: ProjectConfig
+    ) -> None:
+        graph = build_graph(simple_text_config, project_dir)
+        assert "output.txt" in graph.nodes
+        assert graph.number_of_edges() == 0
+
+    def test_chain_dependency(
+        self, project_dir: Path, multi_target_config: ProjectConfig
+    ) -> None:
+        graph = build_graph(multi_target_config, project_dir)
+
+        assert graph.has_edge("input.txt", "summary.md")
+        assert graph.has_edge("summary.md", "final.txt")
+        assert not graph.has_edge("input.txt", "final.txt")
+
+    def test_external_file_as_node(
+        self, project_dir: Path, multi_target_config: ProjectConfig
+    ) -> None:
+        graph = build_graph(multi_target_config, project_dir)
+        assert "input.txt" in graph.nodes
+
+    def test_missing_dependency_raises(
+        self, project_dir: Path, write_config: WriteConfig
+    ) -> None:
+        config = write_config(
+            {"targets": {"out.txt": {"prompt": "x", "inputs": ["nonexistent.txt"]}}}
+        )
+        with pytest.raises(
+            ValueError, match="neither a defined target nor an existing file"
+        ):
+            _ = build_graph(config, project_dir)
+
+    def test_cycle_raises(self, project_dir: Path, write_config: WriteConfig) -> None:
+        config = write_config(
+            {
+                "targets": {
+                    "a.txt": {"prompt": "x", "inputs": ["b.txt"]},
+                    "b.txt": {"prompt": "x", "inputs": ["a.txt"]},
+                }
+            }
+        )
+        with pytest.raises(ValueError, match="cycle"):
+            _ = build_graph(config, project_dir)
+
+    def test_reference_image_creates_edge(
+        self, project_dir: Path, write_config: WriteConfig
+    ) -> None:
+        _ = (project_dir / "ref.png").write_bytes(b"\x89PNG")
+        config = write_config(
+            {"targets": {"out.png": {"prompt": "x", "reference_image": "ref.png"}}}
+        )
+        graph = build_graph(config, project_dir)
+        assert graph.has_edge("ref.png", "out.png")
+
+    def test_control_images_create_edges(
+        self, project_dir: Path, write_config: WriteConfig
+    ) -> None:
+        _ = (project_dir / "ctrl1.png").write_bytes(b"\x89PNG")
+        _ = (project_dir / "ctrl2.png").write_bytes(b"\x89PNG")
+        config = write_config(
+            {
+                "targets": {
+                    "out.png": {
+                        "prompt": "x",
+                        "control_images": ["ctrl1.png", "ctrl2.png"],
+                    }
+                }
+            }
+        )
+        graph = build_graph(config, project_dir)
+        assert graph.has_edge("ctrl1.png", "out.png")
+        assert graph.has_edge("ctrl2.png", "out.png")
+
+    def test_target_depending_on_another_target(
+        self, project_dir: Path, write_config: WriteConfig
+    ) -> None:
+        config = write_config(
+            {
+                "targets": {
+                    "base.txt": {"prompt": "base"},
+                    "derived.txt": {"prompt": "derive", "inputs": ["base.txt"]},
+                }
+            }
+        )
+        graph = build_graph(config, project_dir)
+        assert graph.has_edge("base.txt", "derived.txt")
+
+
+class TestGetBuildOrder:
+    """Test topological generation ordering."""
+
+    def test_independent_targets_same_generation(
+        self, project_dir: Path, write_config: WriteConfig
+    ) -> None:
+        config = write_config(
+            {
+                "targets": {
+                    "a.txt": {"prompt": "x"},
+                    "b.txt": {"prompt": "y"},
+                    "c.png": {"prompt": "z"},
+                }
+            }
+        )
+        graph = build_graph(config, project_dir)
+        order = get_build_order(graph)
+
+        assert len(order) == 1
+        assert set(order[0]) == {"a.txt", "b.txt", "c.png"}
+
+    def test_chain_produces_sequential_generations(
+        self, project_dir: Path, multi_target_config: ProjectConfig
+    ) -> None:
+        graph = build_graph(multi_target_config, project_dir)
+        order = get_build_order(graph)
+
+        # Flatten to find relative positions
+        flat = [name for gen in order for name in gen]
+        assert flat.index("input.txt") < flat.index("summary.md")
+        assert flat.index("summary.md") < flat.index("final.txt")
+
+    def test_diamond_dependency(
+        self, project_dir: Path, write_config: WriteConfig
+    ) -> None:
+        _ = (project_dir / "root.txt").write_text("root")
+        config = write_config(
+            {
+                "targets": {
+                    "left.txt": {"prompt": "x", "inputs": ["root.txt"]},
+                    "right.txt": {"prompt": "y", "inputs": ["root.txt"]},
+                    "merge.txt": {
+                        "prompt": "z",
+                        "inputs": ["left.txt", "right.txt"],
+                    },
+                }
+            }
+        )
+        graph = build_graph(config, project_dir)
+        order = get_build_order(graph)
+        flat = [name for gen in order for name in gen]
+
+        assert flat.index("root.txt") < flat.index("left.txt")
+        assert flat.index("root.txt") < flat.index("right.txt")
+        assert flat.index("left.txt") < flat.index("merge.txt")
+        assert flat.index("right.txt") < flat.index("merge.txt")
+
+
+class TestGetSubgraphForTarget:
+    """Test selective subgraph extraction."""
+
+    def test_subgraph_includes_transitive_deps(
+        self, project_dir: Path, multi_target_config: ProjectConfig
+    ) -> None:
+        graph = build_graph(multi_target_config, project_dir)
+        sub = get_subgraph_for_target(graph, "final.txt")
+
+        assert "final.txt" in sub.nodes
+        assert "summary.md" in sub.nodes
+        assert "input.txt" in sub.nodes
+        # hero.png is independent and should NOT be included
+        assert "hero.png" not in sub.nodes
+
+    def test_subgraph_leaf_target(
+        self, project_dir: Path, multi_target_config: ProjectConfig
+    ) -> None:
+        graph = build_graph(multi_target_config, project_dir)
+        sub = get_subgraph_for_target(graph, "hero.png")
+
+        assert set(sub.nodes) == {"hero.png"}
+
+    def test_subgraph_preserves_edges(
+        self, project_dir: Path, multi_target_config: ProjectConfig
+    ) -> None:
+        graph = build_graph(multi_target_config, project_dir)
+        sub = get_subgraph_for_target(graph, "final.txt")
+
+        assert sub.has_edge("input.txt", "summary.md")
+        assert sub.has_edge("summary.md", "final.txt")