Fold --to/--gen dataset-versioning flags into the dwarf CLI

origin/energy-conservation-poc grew bump-gen/bump-schema --to and
update-manifest --gen flags (091b23a) plus a train output-dir date
prefix (305e436) after the dwarf unification was written locally.
Reconcile: bring plan_bump_gen/plan_bump_schema/plan_update_manifest's
target/target_gen support into the plain-function (argparse-free) form,
thread --to/--gen through scripts/dwarf.py's bump-gen/bump-schema/
update-manifest commands, and take giant/cli.py's date-prefix change
and the associated tests as-is.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/dwarf.py

@@ -175,11 +175,19 @@ def bump_gen(
     date: Annotated[
         Optional[str], typer.Option("--date", help="Override date (default: today, ISO)")
     ] = None,
+    to: Annotated[
+        Optional[str],
+        typer.Option(
+            "--to", metavar="genN", help="Target gen tag (default: one past the current highest)"
+        ),
+    ] = None,
     execute: Annotated[bool, typer.Option("--execute", help="Apply (default: dry run)")] = False,
     root: Annotated[Path, typer.Option("--root", help="Dataset root")] = _DATASET_ROOT_DEFAULT,
 ) -> None:
     """Cut a new raw generation."""
-    run_bump_gen(kind=kind, reason=reason, by=by, date=date, execute=execute, root=str(root))
+    run_bump_gen(
+        kind=kind, reason=reason, by=by, date=date, execute=execute, root=str(root), to=to
+    )
 
 
 @app.command("bump-schema")
@@ -193,12 +201,27 @@ def bump_schema(
     date: Annotated[
         Optional[str], typer.Option("--date", help="Override date (default: today, ISO)")
     ] = None,
+    to: Annotated[
+        Optional[str],
+        typer.Option(
+            "--to",
+            metavar="schemaN",
+            help="Target schema tag (default: one past the current highest)",
+        ),
+    ] = None,
     execute: Annotated[bool, typer.Option("--execute", help="Apply (default: dry run)")] = False,
     root: Annotated[Path, typer.Option("--root", help="Dataset root")] = _DATASET_ROOT_DEFAULT,
 ) -> None:
     """Cut a new schema within a gen."""
     run_bump_schema(
-        kind=kind, gen=gen, reason=reason, by=by, date=date, execute=execute, root=str(root)
+        kind=kind,
+        gen=gen,
+        reason=reason,
+        by=by,
+        date=date,
+        execute=execute,
+        root=str(root),
+        to=to,
     )
 
 
@@ -223,12 +246,18 @@ def update_manifest(
             help="Target schema tag (default: highest schema found in the same gen dir)",
         ),
     ] = None,
+    gen: Annotated[
+        Optional[str],
+        typer.Option("--gen", metavar="genN", help="Target gen tag (default: keep existing gen)"),
+    ] = None,
     execute: Annotated[
         bool, typer.Option("--execute", help="Write updated manifests (default: dry run)")
     ] = False,
 ) -> None:
-    """Repoint manifest(s) to a new schema, verifying all target files exist."""
-    run_update_manifest([str(m) for m in manifests], schema=schema, execute=execute)
+    """Repoint manifest(s) to a new gen and/or schema, verifying all target files exist."""
+    run_update_manifest(
+        [str(m) for m in manifests], schema=schema, execute=execute, gen=gen
+    )
 
 
 @app.command("create-manifest")