test(proxy_behavior): codify G3 (strict-import grep) as a pytest item

Slice 6 of the management-endpoints behavior-pinning effort. Two new tests
walk every .py file under tests/proxy_behavior/ and assert:

  * no ``from litellm.proxy.management_endpoints`` import — the suite is
    deliberately constrained to the HTTP boundary so it survives handler
    refactors;
  * no ``mock``/``patch`` on ``user_api_key_auth`` — mocking auth is the
    structural failure mode of the existing 11k-line mock suite, and the
    point of this harness is that the real auth layer runs.

Codifying G3 as a CI test removes the "did someone forget to check the
PR-description checklist" failure mode.

Plan: https://www.notion.so/36643b8acdab8128a581ced0f6a4744d

tests/proxy_behavior/management/test_no_management_imports.py

@@ -0,0 +1,64 @@
+"""Codify G3 (strict-import grep) as a test.
+
+The behavior-pinning suite asserts at the HTTP boundary against a real proxy
+app. Two forbidden patterns:
+
+1. ``from litellm.proxy.management_endpoints`` — importing handler functions
+   directly turns the suite into unit tests of the handler module rather than
+   behavior tests of the API, and makes the suite brittle to refactors.
+
+2. ``mock``/``patch`` on ``user_api_key_auth`` — mocking auth is the
+   structural failure mode of today's mock-heavy suite. The whole point of the
+   real-DB harness is that auth runs.
+
+Running this as a pytest item means G3 is enforced by CI on every PR, not by
+a checklist someone might forget.
+"""
+
+import pathlib
+import re
+
+import pytest
+
+REPO_ROOT = pathlib.Path(__file__).resolve().parents[3]
+BEHAVIOR_DIR = REPO_ROOT / "tests" / "proxy_behavior"
+
+FORBIDDEN_IMPORT = re.compile(r"^\s*from\s+litellm\.proxy\.management_endpoints\b")
+FORBIDDEN_AUTH_MOCK = re.compile(
+    r"(?:mock\.[A-Za-z_]+|patch[a-z_]*)\([^)]*user_api_key_auth"
+)
+
+# This very file is the one place where the forbidden patterns appear as
+# regex source; exclude it from its own scan so the test is self-checkable.
+SELF = pathlib.Path(__file__).resolve()
+
+
+def _iter_py_files():
+    for path in BEHAVIOR_DIR.rglob("*.py"):
+        if path.resolve() == SELF:
+            continue
+        yield path
+
+
+def test_no_management_endpoint_imports():
+    violations = []
+    for path in _iter_py_files():
+        for lineno, line in enumerate(path.read_text().splitlines(), start=1):
+            if FORBIDDEN_IMPORT.search(line):
+                violations.append(f"{path.relative_to(REPO_ROOT)}:{lineno}: {line.strip()}")
+    assert not violations, (
+        "tests/proxy_behavior/ must not import from litellm.proxy.management_endpoints "
+        "(G3 — assert at the HTTP boundary). Violations:\n  " + "\n  ".join(violations)
+    )
+
+
+def test_no_user_api_key_auth_mocking():
+    violations = []
+    for path in _iter_py_files():
+        for lineno, line in enumerate(path.read_text().splitlines(), start=1):
+            if FORBIDDEN_AUTH_MOCK.search(line):
+                violations.append(f"{path.relative_to(REPO_ROOT)}:{lineno}: {line.strip()}")
+    assert not violations, (
+        "tests/proxy_behavior/ must not mock user_api_key_auth (G3 — auth runs for "
+        "real). Violations:\n  " + "\n  ".join(violations)
+    )