feat: add click-based colorized output with progress events and build timer

- Add click as explicit dependency (already bundled with typer)
- Replace typer.echo calls with click.echo + click.style for colorized output
- Add BuildEvent enum and ProgressCallback to builder for decoupled progress reporting
- Remove direct typer dependency from builder module
- Show per-target status with colored labels (skip/ok/fail/...)
- Display elapsed build time in summary
- Colorize graph and clean command output
- Update CLI tests to match new output format

bulkgen/cli.py

@@ -3,13 +3,15 @@
 from __future__ import annotations
 
 import asyncio
+import time
 from pathlib import Path
 from typing import Annotated
 
+import click
 import typer
 
-from bulkgen.builder import run_build
-from bulkgen.config import load_config
+from bulkgen.builder import BuildEvent, BuildResult, run_build
+from bulkgen.config import ProjectConfig, load_config
 from bulkgen.graph import build_graph, get_build_order
 
 app = typer.Typer(name="bulkgen", help="AI artifact build tool.")
@@ -19,15 +21,76 @@ 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)
+        click.echo(
+            click.style("Error: ", fg="red", bold=True)
+            + "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)
+        click.echo(
+            click.style("Error: ", fg="red", bold=True)
+            + f"Multiple .bulkgen.yaml files found: {names}",
+            err=True,
+        )
         raise typer.Exit(code=1)
     return candidates[0]
 
 
+def _format_elapsed(seconds: float) -> str:
+    """Format elapsed time as a human-readable string."""
+    if seconds < 60:
+        return f"{seconds:.1f}s"
+    minutes = int(seconds // 60)
+    secs = seconds % 60
+    return f"{minutes}m{secs:.1f}s"
+
+
+def _run_build(
+    config: ProjectConfig, project_dir: Path, target: str | None
+) -> tuple[BuildResult, float]:
+    """Run the async build with click-styled progress output and timing."""
+
+    def on_progress(event: BuildEvent, name: str, detail: str) -> None:
+        if event is BuildEvent.TARGET_SKIPPED:
+            click.echo(
+                click.style("  skip ", fg="yellow")
+                + click.style(name, bold=True)
+                + click.style(f"  ({detail})", dim=True)
+            )
+        elif event is BuildEvent.TARGET_BUILDING:
+            click.echo(click.style("  ... ", fg="cyan") + click.style(name, bold=True))
+        elif event is BuildEvent.TARGET_OK:
+            click.echo(click.style("   ok ", fg="green") + click.style(name, bold=True))
+        elif event is BuildEvent.TARGET_FAILED:
+            click.echo(
+                click.style(" fail ", fg="red", bold=True)
+                + click.style(name, bold=True)
+                + f"  {detail}"
+            )
+        elif event is BuildEvent.TARGET_DEP_FAILED:
+            click.echo(
+                click.style(" fail ", fg="red")
+                + click.style(name, bold=True)
+                + click.style(f"  ({detail})", dim=True)
+            )
+        elif event is BuildEvent.TARGET_NO_PROVIDER:
+            click.echo(
+                click.style(" fail ", fg="red", bold=True)
+                + click.style(name, bold=True)
+                + f"  {detail}"
+            )
+
+    start = time.monotonic()
+    result = asyncio.run(
+        run_build(config, project_dir, target, on_progress=on_progress)
+    )
+    elapsed = time.monotonic() - start
+
+    return result, elapsed
+
+
 @app.command()
 def build(
     target: Annotated[
@@ -39,16 +102,25 @@ def build(
     config_path = _find_config(project_dir)
     config = load_config(config_path)
 
-    result = asyncio.run(run_build(config, project_dir, target))
+    click.echo(click.style("bulkgen", fg="cyan", bold=True) + " building targets...\n")
 
+    result, elapsed = _run_build(config, project_dir, target)
+
+    # Summary
+    click.echo("")
+    parts: list[str] = []
     if result.built:
-        typer.echo(f"\nBuilt {len(result.built)} target(s)")
+        parts.append(click.style(f"{len(result.built)} built", fg="green", bold=True))
     if result.skipped:
-        typer.echo(f"Skipped {len(result.skipped)} target(s) (up to date)")
+        parts.append(click.style(f"{len(result.skipped)} skipped", fg="yellow"))
+    if result.failed:
+        parts.append(click.style(f"{len(result.failed)} failed", fg="red", bold=True))
+
+    summary = ", ".join(parts) if parts else click.style("nothing to do", dim=True)
+    timer = click.style(f" in {_format_elapsed(elapsed)}", dim=True)
+    click.echo(summary + timer)
+
     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)
 
 
@@ -64,15 +136,15 @@ def clean() -> None:
         target_path = project_dir / target_name
         if target_path.exists():
             target_path.unlink()
-            typer.echo(f"Removed: {target_name}")
+            click.echo(click.style("  rm ", fg="red") + target_name)
             removed += 1
 
     state_path = project_dir / ".bulkgen.state.yaml"
     if state_path.exists():
         state_path.unlink()
-        typer.echo("Removed: .bulkgen.state.yaml")
+        click.echo(click.style("  rm ", fg="red") + ".bulkgen.state.yaml")
 
-    typer.echo(f"Cleaned {removed} artifact(s)")
+    click.echo(click.style(f"\nCleaned {removed} artifact(s)", bold=True))
 
 
 @app.command()
@@ -91,11 +163,16 @@ def graph() -> None:
         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)}")
+            label = click.style(f"Stage {i}", fg="cyan", bold=True)
+            kind = click.style(" (inputs)", dim=True)
+            click.echo(f"{label}{kind}: {', '.join(externals_in_gen)}")
         if targets_in_gen:
-            typer.echo(f"Stage {i} (targets): {', '.join(targets_in_gen)}")
+            label = click.style(f"Stage {i}", fg="green", bold=True)
+            kind = click.style(" (targets)", dim=True)
+            click.echo(f"{label}{kind}: {', '.join(targets_in_gen)}")
 
         for node in gen:
             preds: list[str] = list(dep_graph.predecessors(node))
             if preds:
-                typer.echo(f"  {node} <- {', '.join(preds)}")
+                arrow = click.style(" <- ", dim=True)
+                click.echo(f"  {node}{arrow}{', '.join(preds)}")