perf(1.1): lazy topology.generate re-export (C2)

topology/__init__ eagerly imported generator -> allocator -> repository ->
the full SQLModel ORM. Defer via PEP 562 __getattr__ so importing the
package doesn't drag the DB layer into DB-less workers. Public API
(from decnet.topology import generate) unchanged. Guard test locks it in.

decnet/topology/__init__.py

@@ -7,7 +7,6 @@ is marked as the DMZ (Internet-facing).  Persisted via the repo pattern;
 deployed via :mod:`decnet.engine.deployer`.
 """
 from decnet.topology.config import TopologyConfig, GeneratedTopology
-from decnet.topology.generator import generate
 from decnet.topology.status import (
     TopologyStatus,
     assert_transition,
@@ -22,3 +21,14 @@ __all__ = [
     "assert_transition",
     "TopologyStatusError",
 ]
+
+
+def __getattr__(name: str):
+    # ponytail: lazy re-export — `generate` pulls generator→allocator→repository→the
+    # full SQLModel ORM (~38MB). Defer it so importing this package (which every worker
+    # does transitively via the CLI) doesn't drag the DB layer into DB-less workers.
+    if name == "generate":
+        from decnet.topology.generator import generate
+
+        return generate
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")

tests/topology/test_lazy_imports.py

@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+"""Guard: importing the topology package must not eagerly pull the generator
+(which drags the full SQLModel ORM, ~38MB, into every worker via the CLI).
+
+See development/RELEASE-1.1.md (C2).
+"""
+import subprocess
+import sys
+
+
+def _import_and_report(stmt: str) -> set[str]:
+    """Run `stmt` in a fresh interpreter, return the set of decnet.* modules loaded."""
+    code = (
+        f"import sys\n{stmt}\n"
+        "print('\\n'.join(m for m in sys.modules if m.startswith('decnet')))"
+    )
+    out = subprocess.run(
+        [sys.executable, "-c", code], capture_output=True, text=True, check=True
+    )
+    return set(out.stdout.split())
+
+
+def test_topology_import_does_not_pull_generator():
+    loaded = _import_and_report("import decnet.topology")
+    assert "decnet.topology.generator" not in loaded, (
+        "topology/__init__ regressed to eager generator import — this pulls the "
+        "repository → SQLModel ORM into every DB-less worker"
+    )
+
+
+def test_generate_still_resolvable_lazily():
+    loaded = _import_and_report("from decnet.topology import generate")
+    assert "decnet.topology.generator" in loaded  # accessing it loads it
+    # and it's actually callable
+    from decnet.topology import generate
+
+    assert callable(generate)