feat: sap-cli skill v2.1.0 — self-contained distributable package

- assets/: sap-cli source (v2.1.0, 26 commands, 16 object types)
- references/: tool constraints + error handling (self-contained)
- scripts/setup.py: one-click install/config/verify
- SKILL.md: full command reference + dual-platform install guide
- VERSION: 2.1.0

Built from D:/Codespace/sap-cli via scripts/pack_skill.py

assets/sapcli/client/__init__.py

@@ -0,0 +1,29 @@
+"""sapcli.client — ADT client split into Mixin modules.
+
+Usage::
+
+    from sapcli.client import ADTClient
+
+The public API is identical to the original monolithic ``client.py``.
+"""
+
+from sapcli.client._base import ADTClientBase
+from sapcli.client._source import SourceMixin
+from sapcli.client._transport import TransportMixin
+from sapcli.client._search import SearchMixin
+from sapcli.client._ddic import DdicMixin
+
+
+class ADTClient(
+    ADTClientBase,
+    SourceMixin,
+    TransportMixin,
+    SearchMixin,
+    DdicMixin,
+):
+    """Full ADT client composed from domain-specific Mixins."""
+
+    pass
+
+
+__all__ = ["ADTClient"]