Add declarative Flow CLI support (#6294)

* Add declarative Flow CLI support

Currently, declarative flows can be loaded by the runtime, but the CLI
still treats them as an experimental definition file instead of a
first-class Flow project shape.

With this PR, `crewai create flow --declarative` scaffolds a YAML-backed
Flow project, and `crewai run`, `crewai flow kickoff`, and `crewai flow
plot` can run against the configured definition.

This also lets crew actions reference reusable crew definition files or
folders and override their inputs from the Flow definition, so
declarative flows can compose existing declarative crews without
inlining everything.

* Address code review comments

lib/cli/src/crewai_cli/plot_flow.py

@@ -5,19 +5,27 @@ import click
 
 def plot_flow() -> None:
     """
-    Plot the flow by running a command in the UV environment.
+    Plot the flow from declarative config or the Python UV entrypoint.
     """
-    command = ["uv", "run", "plot"]
+    from crewai_cli.run_declarative_flow import (
+        configured_project_declarative_flow,
+        plot_declarative_flow_in_project_env,
+    )
 
-    try:
-        result = subprocess.run(command, capture_output=False, text=True, check=True)  # noqa: S603
+    if definition := configured_project_declarative_flow():
+        plot_declarative_flow_in_project_env(definition)
+    else:
+        command = ["uv", "run", "plot"]
 
-        if result.stderr:
-            click.echo(result.stderr, err=True)
+        try:
+            subprocess.run(  # noqa: S603
+                command, capture_output=False, text=True, check=True
+            )
 
-    except subprocess.CalledProcessError as e:
-        click.echo(f"An error occurred while plotting the flow: {e}", err=True)
-        click.echo(e.output, err=True)
+        except subprocess.CalledProcessError as e:
+            click.echo(f"An error occurred while plotting the flow: {e}", err=True)
+            raise SystemExit(1) from e
 
-    except Exception as e:
-        click.echo(f"An unexpected error occurred: {e}", err=True)
+        except Exception as e:
+            click.echo(f"An unexpected error occurred: {e}", err=True)
+            raise SystemExit(1) from e