feat: add CLI commands (build, clean, graph)

- build: executes all or specific target with dependency resolution
- clean: removes generated artifacts and state file, preserves inputs
- graph: prints dependency graph with build stages
- Config discovery: finds single *.bulkgen.yaml in working directory

bulkgen/cli.py

@@ -0,0 +1,101 @@
+"""Typer CLI for bulkgen: build, clean, graph commands."""
+
+from __future__ import annotations
+
+import asyncio
+from pathlib import Path
+from typing import Annotated
+
+import typer
+
+from bulkgen.builder import run_build
+from bulkgen.config import load_config
+from bulkgen.graph import build_graph, get_build_order
+
+app = typer.Typer(name="bulkgen", help="AI artifact build tool.")
+
+
+def _find_config(directory: Path) -> Path:
+    """Find the single ``*.bulkgen.yaml`` file in *directory*."""
+    candidates = list(directory.glob("*.bulkgen.yaml"))
+    if len(candidates) == 0:
+        typer.echo("Error: No .bulkgen.yaml file found in current directory", err=True)
+        raise typer.Exit(code=1)
+    if len(candidates) > 1:
+        names = ", ".join(str(c.name) for c in candidates)
+        typer.echo(f"Error: Multiple .bulkgen.yaml files found: {names}", err=True)
+        raise typer.Exit(code=1)
+    return candidates[0]
+
+
+@app.command()
+def build(
+    target: Annotated[
+        str | None, typer.Argument(help="Specific target to build.")
+    ] = None,
+) -> None:
+    """Build all targets (or a specific target) in dependency order."""
+    project_dir = Path.cwd()
+    config_path = _find_config(project_dir)
+    config = load_config(config_path)
+
+    result = asyncio.run(run_build(config, project_dir, target))
+
+    if result.built:
+        typer.echo(f"\nBuilt {len(result.built)} target(s)")
+    if result.skipped:
+        typer.echo(f"Skipped {len(result.skipped)} target(s) (up to date)")
+    if result.failed:
+        typer.echo(f"Failed {len(result.failed)} target(s):", err=True)
+        for name, err in result.failed.items():
+            typer.echo(f"  {name}: {err}", err=True)
+        raise typer.Exit(code=1)
+
+
+@app.command()
+def clean() -> None:
+    """Remove generated artifacts (targets only, not input files)."""
+    project_dir = Path.cwd()
+    config_path = _find_config(project_dir)
+    config = load_config(config_path)
+
+    removed = 0
+    for target_name in config.targets:
+        target_path = project_dir / target_name
+        if target_path.exists():
+            target_path.unlink()
+            typer.echo(f"Removed: {target_name}")
+            removed += 1
+
+    state_path = project_dir / ".bulkgen.state.yaml"
+    if state_path.exists():
+        state_path.unlink()
+        typer.echo("Removed: .bulkgen.state.yaml")
+
+    typer.echo(f"Cleaned {removed} artifact(s)")
+
+
+@app.command()
+def graph() -> None:
+    """Print the dependency graph with build stages."""
+    project_dir = Path.cwd()
+    config_path = _find_config(project_dir)
+    config = load_config(config_path)
+
+    dep_graph = build_graph(config, project_dir)
+    generations = get_build_order(dep_graph)
+    target_names = set(config.targets)
+
+    for i, gen in enumerate(generations):
+        targets_in_gen = [n for n in gen if n in target_names]
+        externals_in_gen = [n for n in gen if n not in target_names]
+
+        if externals_in_gen:
+            typer.echo(f"Stage {i} (inputs): {', '.join(externals_in_gen)}")
+        if targets_in_gen:
+            typer.echo(f"Stage {i} (targets): {', '.join(targets_in_gen)}")
+
+        for node in gen:
+            predecessors = list(dep_graph.predecessors(node))
+            if predecessors:
+                typer.echo(f"  {node} <- {', '.join(predecessors)}")