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_state.py

@@ -10,13 +10,15 @@ from bulkgen.state import (
     BuildState,
     TargetState,
     hash_file,
-    hash_string,
     is_target_dirty,
     load_state,
     record_target_state,
     save_state,
+    state_filename,
 )
 
+_PROJECT = "test"
+
 
 class TestHashFunctions:
     """Test hashing helpers."""
@@ -34,18 +36,22 @@ class TestHashFunctions:
         h2 = hash_file(f)
         assert h1 != h2
 
-    def test_hash_string_deterministic(self) -> None:
-        assert hash_string("abc") == hash_string("abc")
 
-    def test_hash_string_differs(self) -> None:
-        assert hash_string("abc") != hash_string("xyz")
+class TestStateFilename:
+    """Test state filename derivation."""
+
+    def test_state_filename(self) -> None:
+        assert state_filename("cards") == ".cards.bulkgen-state.yaml"
+
+    def test_state_filename_simple(self) -> None:
+        assert state_filename("project") == ".project.bulkgen-state.yaml"
 
 
 class TestStatePersistence:
     """Test save/load round-trip of build state."""
 
     def test_load_missing_file_returns_empty(self, project_dir: Path) -> None:
-        state = load_state(project_dir)
+        state = load_state(project_dir, _PROJECT)
         assert state.targets == {}
 
     def test_save_and_load_round_trip(self, project_dir: Path) -> None:
@@ -53,40 +59,36 @@ class TestStatePersistence:
             targets={
                 "out.txt": TargetState(
                     input_hashes={"dep.txt": "abc123"},
-                    prompt_hash="prompt_hash_val",
+                    prompt="Generate something",
                     model="mistral-large-latest",
-                    extra_hash="",
+                    extra_params={},
                 )
             }
         )
-        save_state(state, project_dir)
-        loaded = load_state(project_dir)
+        save_state(state, project_dir, _PROJECT)
+        loaded = load_state(project_dir, _PROJECT)
 
         assert loaded.targets["out.txt"].model == "mistral-large-latest"
         assert loaded.targets["out.txt"].input_hashes == {"dep.txt": "abc123"}
-        assert loaded.targets["out.txt"].prompt_hash == "prompt_hash_val"
+        assert loaded.targets["out.txt"].prompt == "Generate something"
 
     def test_load_empty_yaml(self, project_dir: Path) -> None:
-        _ = (project_dir / ".bulkgen.state.yaml").write_text("")
-        state = load_state(project_dir)
+        _ = (project_dir / state_filename(_PROJECT)).write_text("")
+        state = load_state(project_dir, _PROJECT)
         assert state.targets == {}
 
     def test_save_overwrites_existing(self, project_dir: Path) -> None:
         state1 = BuildState(
-            targets={
-                "a.txt": TargetState(input_hashes={}, prompt_hash="h1", model="m1")
-            }
+            targets={"a.txt": TargetState(input_hashes={}, prompt="p1", model="m1")}
         )
-        save_state(state1, project_dir)
+        save_state(state1, project_dir, _PROJECT)
 
         state2 = BuildState(
-            targets={
-                "b.txt": TargetState(input_hashes={}, prompt_hash="h2", model="m2")
-            }
+            targets={"b.txt": TargetState(input_hashes={}, prompt="p2", model="m2")}
         )
-        save_state(state2, project_dir)
+        save_state(state2, project_dir, _PROJECT)
 
-        loaded = load_state(project_dir)
+        loaded = load_state(project_dir, _PROJECT)
         assert "b.txt" in loaded.targets
         assert "a.txt" not in loaded.targets
 
@@ -95,16 +97,16 @@ class TestStatePersistence:
             targets={
                 "out.txt": TargetState(
                     input_hashes={"f.txt": "hash"},
-                    prompt_hash="ph",
+                    prompt="do something",
                     model="m",
-                    extra_hash="eh",
+                    extra_params={"width": 512},
                 )
             }
         )
-        save_state(state, project_dir)
+        save_state(state, project_dir, _PROJECT)
 
         raw: object = yaml.safe_load(  # pyright: ignore[reportAny]
-            (project_dir / ".bulkgen.state.yaml").read_text()
+            (project_dir / state_filename(_PROJECT)).read_text()
         )
         assert isinstance(raw, dict)
         assert "targets" in raw
@@ -296,9 +298,9 @@ class TestRecordAndDirtyRoundTrip:
             state=state,
             project_dir=project_dir,
         )
-        save_state(state, project_dir)
+        save_state(state, project_dir, _PROJECT)
 
-        loaded_state = load_state(project_dir)
+        loaded_state = load_state(project_dir, _PROJECT)
         assert not is_target_dirty(
             "result.md",
             resolved_prompt="do the thing",