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

bulkgen/cli.py

@@ -14,9 +14,21 @@ from bulkgen.builder import BuildEvent, BuildResult, run_build
 from bulkgen.config import ProjectConfig, load_config
 from bulkgen.graph import build_graph, get_build_order
 from bulkgen.providers.registry import get_all_models
+from bulkgen.state import state_filename
 
 app = typer.Typer(name="bulkgen", help="AI artifact build tool.")
 
+_CONFIG_SUFFIX = ".bulkgen.yaml"
+
+
+def _project_name(config_path: Path) -> str:
+    """Derive the project name from a config path.
+
+    ``cards.bulkgen.yaml`` → ``cards``
+    """
+    name = config_path.name
+    return name.removesuffix(_CONFIG_SUFFIX)
+
 
 def _find_config(directory: Path) -> Path:
     """Find the single ``*.bulkgen.yaml`` file in *directory*."""
@@ -49,7 +61,7 @@ def _format_elapsed(seconds: float) -> str:
 
 
 def _run_build(
-    config: ProjectConfig, project_dir: Path, target: str | None
+    config: ProjectConfig, project_dir: Path, project_name: str, target: str | None
 ) -> tuple[BuildResult, float]:
     """Run the async build with click-styled progress output and timing."""
 
@@ -85,7 +97,7 @@ def _run_build(
 
     start = time.monotonic()
     result = asyncio.run(
-        run_build(config, project_dir, target, on_progress=on_progress)
+        run_build(config, project_dir, project_name, target, on_progress=on_progress)
     )
     elapsed = time.monotonic() - start
 
@@ -102,10 +114,11 @@ def build(
     project_dir = Path.cwd()
     config_path = _find_config(project_dir)
     config = load_config(config_path)
+    name = _project_name(config_path)
 
     click.echo(click.style("bulkgen", fg="cyan", bold=True) + " building targets...\n")
 
-    result, elapsed = _run_build(config, project_dir, target)
+    result, elapsed = _run_build(config, project_dir, name, target)
 
     # Summary
     click.echo("")
@@ -131,6 +144,7 @@ def clean() -> None:
     project_dir = Path.cwd()
     config_path = _find_config(project_dir)
     config = load_config(config_path)
+    state_name = state_filename(_project_name(config_path))
 
     removed = 0
     for target_name in config.targets:
@@ -140,10 +154,10 @@ def clean() -> None:
             click.echo(click.style("  rm ", fg="red") + target_name)
             removed += 1
 
-    state_path = project_dir / ".bulkgen.state.yaml"
+    state_path = project_dir / state_name
     if state_path.exists():
         state_path.unlink()
-        click.echo(click.style("  rm ", fg="red") + ".bulkgen.state.yaml")
+        click.echo(click.style("  rm ", fg="red") + state_name)
 
     click.echo(click.style(f"\nCleaned {removed} artifact(s)", bold=True))