[pipeline & req]: implement pdf2model with DataFlex training backend; add pdf2model-dataflex dependency group

dataflow/cli.py

@@ -330,22 +330,47 @@ def eval_local_cmd():
 def pdf2model_init(cache: Path = typer.Option(Path("."), 
                    help = "Cache dir"),
                    qa: str = typer.Option("kbc", help="Which pipeline to init (vqa or kbc)"),
-                   model: Optional[str] = typer.Option(None, help="Base model name or path")):
+                   model: Optional[str] = typer.Option(None, help="Base model name or path"),
+                   train_backend: str = typer.Option(
+                       "base",
+                       "--train-backend",
+                       help="With --qa kbc: 'base' (LlamaFactory) or a registered dataflex-* backend (see cli_pdf.DATAFLEX_BACKEND_SPECS). vqa only allows 'base'.",
+                   )):
     if qa not in ["vqa", "kbc"]:
         _echo(f"Invalid qa type: {qa}. Must be 'vqa' or 'kbc'.", "red")
         raise typer.Exit(code=1)
-
+    if qa == "vqa":
+        if train_backend != "base":
+            _echo("vqa only supports --train-backend base.", "red")
+            raise typer.Exit(code=1)
+    else:
+        from dataflow.cli_funcs.cli_pdf import DATAFLEX_BACKEND_SPECS  # type: ignore
+
+        allowed_kbc = {"base", *DATAFLEX_BACKEND_SPECS.keys()}
+        if train_backend not in allowed_kbc:
+            supported = ", ".join(sorted(allowed_kbc))
+            _echo(
+                f"Invalid --train-backend={train_backend!r} for --qa kbc. Supported: {supported}.",
+                "red",
+            )
+            raise typer.Exit(code=1)
+
     try:
         from dataflow.cli_funcs.cli_pdf import cli_pdf2model_init  # type: ignore
-        cli_pdf2model_init(cache_path=str(cache), qa_type=qa, model_name=model)
+        cli_pdf2model_init(
+            cache_path=str(cache),
+            qa_type=qa,
+            model_name=model,
+            pdf2model_train_backend=train_backend,
+        )
     except Exception as e:
         _echo(f"pdf2model init error: {e}", "red")
         raise typer.Exit(code=1)
 
 
 @pdf_app.command("train")
 def pdf2model_train(cache: Path = typer.Option(Path("."), help="Cache dir"),
-                    lf_yaml: Optional[Path] = typer.Option(None, help="LlamaFactory yaml")):
+                    lf_yaml: Optional[Path] = typer.Option(None, help="LlamaFactory yaml (base backend only)")):
 
     try:
         from dataflow.cli_funcs.cli_pdf import cli_pdf2model_train  # type: ignore