Improve crewai run startup UX (#6297)

Remove redundant startup logs from `crewai run` and make the legacy flow
command warning actionable.

- Stop printing `Running the Flow` and `Running the Crew` before project
  execution.
- Stop printing the redundant `Flow started with ID: ...` line while
  preserving flow lifecycle event emission.
- Replace Click's generic `kickoff` deprecation warning with a clearer
  message that tells users to use `crewai run`.

lib/cli/tests/test_run_crew.py

@@ -622,7 +622,7 @@ def test_run_crew_runs_classic_crew_project(monkeypatch, capsys):
 
     run_crew_module.run_crew(trained_agents_file="trained.pkl")
 
-    assert capsys.readouterr().out == "Running the Crew\n"
+    assert capsys.readouterr().out == ""
     assert calls == [
         (
             "run_crew",
@@ -648,7 +648,7 @@ def test_run_crew_runs_python_flow_project(monkeypatch, capsys):
 
     run_crew_module.run_crew()
 
-    assert capsys.readouterr().out == "Running the Flow\n"
+    assert capsys.readouterr().out == ""
     assert calls == [("kickoff", {"entity_type": "flow"})]
 
 
@@ -694,5 +694,5 @@ def test_run_crew_runs_configured_declarative_flow_project(monkeypatch, capsys):
 
     run_crew_module.run_crew()
 
-    assert capsys.readouterr().out == "Running the Flow\n"
+    assert capsys.readouterr().out == ""
     assert calls == [("flow.yaml", None)]