Merge system-optimization IR contracts and retire legacy engine adapter

app/simulation/ir/compiler.py

@@ -0,0 +1,14 @@
+"""Retired object-engine IR adapter; the independent v2 schema is retained.
+
+Current native execution is generated by native_codegen.compile_native_program.
+It does not yet emit the separate System IR v2 execution-plan format.
+"""
+
+
+def compile_system_ir(*args, **kwargs):
+    """Fail explicitly for callers of the removed GenericFluidSystem adapter."""
+    raise NotImplementedError(
+        "The GenericFluidSystem to System IR v2 exporter was retired with the Python "
+        "numerical engine. Use native_codegen.compiler.compile_native_program(network) "
+        "for the current C executable path. System IR v2 schema and validation remain available."
+    )