refactor(tests): centralize fake endpoint resolver cleanup

Test-only refactor continuing #2523. Centralizes the final repeated fake src.endpoint_resolver cleanup pattern into a focused import-state helper.

tests/helpers/import_state.py

@@ -12,6 +12,11 @@ Use ``clear_fake_database_modules`` to evict a *stubbed* ``core.database`` (and
 its companion ``src.database``) that another test left in import state, without
 touching a real ``core.database`` loaded from disk.
 
+Use ``clear_fake_endpoint_resolver_modules`` to evict a *stubbed*
+``src.endpoint_resolver`` (and the route modules that imported it) that another
+test left in import state, without touching a real ``src.endpoint_resolver``
+loaded from disk.
+
 Background: importing ``routes.session_routes`` also sets ``session_routes`` on
 the parent ``routes`` package object. A ``from routes import session_routes``
 or ``import routes.session_routes as X`` statement resolves through that parent
@@ -93,6 +98,50 @@ def clear_fake_database_modules():
         delattr(parent, "database")
 
 
+def clear_fake_endpoint_resolver_modules(*extra_modules):
+    """Evict a *stubbed* ``src.endpoint_resolver`` (and dependent route modules).
+
+    Test-only. Several route tests need the *real* ``src.endpoint_resolver`` URL
+    helpers, but another test may have installed a fake — a stub module with no
+    on-disk ``__file__`` — into ``sys.modules`` and onto the ``src`` package
+    during collection. The route modules (``routes.model_routes`` and any extras
+    passed in, e.g. ``routes.chat_routes``) get cached against that fake on first
+    import, so they must be evicted too.
+
+    Conservative, mirroring ``clear_fake_database_modules`` and the per-file
+    guards it replaces:
+
+    * It acts only when ``src.endpoint_resolver`` is a fake/stub, detected by a
+      falsy ``__file__`` (missing, ``None``, or empty string) — exactly the
+      truthiness check the old inline guards used. A real resolver loaded from
+      disk carries a truthy ``__file__`` and is left untouched, as is the case
+      where nothing is cached. When the resolver is real, the dependent route
+      modules are left untouched too.
+    * When it does act, it drops ``routes.model_routes`` plus every name in
+      ``extra_modules``.
+    * It removes the ``src.endpoint_resolver`` parent-package attribute only when
+      that attribute is the same fake object being evicted.
+
+    Behavior delta vs. the old bare ``sys.modules.pop(...)`` guards: dependent
+    modules are dropped via :func:`clear_module`, which also clears the parent
+    ``routes`` package attribute (e.g. ``routes.model_routes``), not just the
+    ``sys.modules`` entry. This prevents a stale parent attribute from shadowing
+    the fresh import — the same parent-attr handling the rest of this helper
+    family already applies.
+    """
+    parent = sys.modules.get("src")
+    attr = getattr(parent, "endpoint_resolver", None) if parent is not None else None
+    mod = sys.modules.get("src.endpoint_resolver") or attr
+    if mod is None or getattr(mod, "__file__", None):
+        return
+    sys.modules.pop("src.endpoint_resolver", None)
+    if parent is not None and attr is mod:
+        delattr(parent, "endpoint_resolver")
+    clear_module("routes.model_routes")
+    for name in extra_modules:
+        clear_module(name)
+
+
 @contextmanager
 def preserve_import_state(*module_names):
     """Save and restore sys.modules entries and parent-package attributes.