refactor: use project-named state file and store prompt/params directly

- State filename now derives from config: cards.bulkgen.yaml produces
  .cards.bulkgen-state.yaml instead of .bulkgen.state.yaml
- Store resolved prompt text and extra params directly in state file
  instead of hashing them, making state files human-readable
- Only file input contents remain hashed (SHA-256)
- Thread project_name through builder and CLI
- Remove hash_string() and _extra_hash() helpers
- Update .gitignore pattern to .*.bulkgen-state.yaml

tests/test_builder.py

@@ -23,6 +23,8 @@ from bulkgen.state import load_state
 
 WriteConfig = Callable[[dict[str, object]], ProjectConfig]
 
+_PROJECT = "project"
+
 
 _FAKE_TEXT_MODELS = [
     ModelInfo(
@@ -196,7 +198,7 @@ class TestRunBuild:
         self, project_dir: Path, simple_text_config: ProjectConfig
     ) -> None:
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
-            result = await run_build(simple_text_config, project_dir)
+            result = await run_build(simple_text_config, project_dir, _PROJECT)
 
         assert result.built == ["output.txt"]
         assert result.skipped == []
@@ -207,7 +209,7 @@ class TestRunBuild:
         self, project_dir: Path, multi_target_config: ProjectConfig
     ) -> None:
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
-            result = await run_build(multi_target_config, project_dir)
+            result = await run_build(multi_target_config, project_dir, _PROJECT)
 
         assert "summary.md" in result.built
         assert "final.txt" in result.built
@@ -222,10 +224,10 @@ class TestRunBuild:
         self, project_dir: Path, simple_text_config: ProjectConfig
     ) -> None:
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
-            result1 = await run_build(simple_text_config, project_dir)
+            result1 = await run_build(simple_text_config, project_dir, _PROJECT)
             assert result1.built == ["output.txt"]
 
-            result2 = await run_build(simple_text_config, project_dir)
+            result2 = await run_build(simple_text_config, project_dir, _PROJECT)
             assert result2.skipped == ["output.txt"]
             assert result2.built == []
 
@@ -234,11 +236,11 @@ class TestRunBuild:
     ) -> None:
         config1 = write_config({"targets": {"out.txt": {"prompt": "version 1"}}})
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
-            r1 = await run_build(config1, project_dir)
+            r1 = await run_build(config1, project_dir, _PROJECT)
             assert r1.built == ["out.txt"]
 
             config2 = write_config({"targets": {"out.txt": {"prompt": "version 2"}}})
-            r2 = await run_build(config2, project_dir)
+            r2 = await run_build(config2, project_dir, _PROJECT)
             assert r2.built == ["out.txt"]
 
     async def test_rebuild_after_input_change(
@@ -249,11 +251,11 @@ class TestRunBuild:
             {"targets": {"out.md": {"prompt": "x", "inputs": ["data.txt"]}}}
         )
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
-            r1 = await run_build(config, project_dir)
+            r1 = await run_build(config, project_dir, _PROJECT)
             assert r1.built == ["out.md"]
 
             _ = (project_dir / "data.txt").write_text("modified")
-            r2 = await run_build(config, project_dir)
+            r2 = await run_build(config, project_dir, _PROJECT)
             assert r2.built == ["out.md"]
 
     async def test_selective_build_single_target(
@@ -261,7 +263,7 @@ class TestRunBuild:
     ) -> None:
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
             result = await run_build(
-                multi_target_config, project_dir, target="summary.md"
+                multi_target_config, project_dir, _PROJECT, target="summary.md"
             )
 
         assert "summary.md" in result.built
@@ -274,7 +276,7 @@ class TestRunBuild:
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
             with pytest.raises(ValueError, match="Unknown target"):
                 _ = await run_build(
-                    simple_text_config, project_dir, target="nonexistent.txt"
+                    simple_text_config, project_dir, _PROJECT, target="nonexistent.txt"
                 )
 
     async def test_failed_target_isolates_independent(
@@ -322,7 +324,7 @@ class TestRunBuild:
             "bulkgen.builder._create_providers",
             return_value=[routing_provider, FakeImageProvider()],
         ):
-            result = await run_build(config, project_dir)
+            result = await run_build(config, project_dir, _PROJECT)
 
         assert "fail.txt" in result.failed
         assert "ok.txt" in result.built
@@ -343,7 +345,7 @@ class TestRunBuild:
             "bulkgen.builder._create_providers",
             return_value=[FailingTextProvider(), FakeImageProvider()],
         ):
-            result = await run_build(config, project_dir)
+            result = await run_build(config, project_dir, _PROJECT)
 
         assert "base.txt" in result.failed
         assert "child.txt" in result.failed
@@ -356,7 +358,7 @@ class TestRunBuild:
             "bulkgen.builder._create_providers",
             return_value=[],
         ):
-            result = await run_build(simple_text_config, project_dir)
+            result = await run_build(simple_text_config, project_dir, _PROJECT)
 
         assert "output.txt" in result.failed
         assert "No provider available" in result.failed["output.txt"]
@@ -373,9 +375,9 @@ class TestRunBuild:
             }
         )
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
-            _ = await run_build(config, project_dir)
+            _ = await run_build(config, project_dir, _PROJECT)
 
-        state = load_state(project_dir)
+        state = load_state(project_dir, _PROJECT)
         assert "a.txt" in state.targets
         assert "b.txt" in state.targets
 
@@ -385,7 +387,7 @@ class TestRunBuild:
         config = write_config({"targets": {"out.txt": {"prompt": prompt_file.name}}})
 
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
-            result = await run_build(config, project_dir)
+            result = await run_build(config, project_dir, _PROJECT)
 
         assert result.built == ["out.txt"]
         content = (project_dir / "out.txt").read_text()
@@ -395,12 +397,12 @@ class TestRunBuild:
         self, project_dir: Path, simple_text_config: ProjectConfig
     ) -> None:
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
-            r1 = await run_build(simple_text_config, project_dir)
+            r1 = await run_build(simple_text_config, project_dir, _PROJECT)
             assert r1.built == ["output.txt"]
 
             (project_dir / "output.txt").unlink()
 
-            r2 = await run_build(simple_text_config, project_dir)
+            r2 = await run_build(simple_text_config, project_dir, _PROJECT)
             assert r2.built == ["output.txt"]
 
     async def test_diamond_dependency_all_built(
@@ -420,7 +422,7 @@ class TestRunBuild:
             }
         )
         with patch("bulkgen.builder._create_providers", return_value=_fake_providers()):
-            result = await run_build(config, project_dir)
+            result = await run_build(config, project_dir, _PROJECT)
 
         assert set(result.built) == {"left.md", "right.md", "merge.txt"}
         assert result.failed == {}