Review fixes: persisted flow-user admin seed and real cv.multi_select

Review rounds 1-2 (Codex gpt-5.6-terra) found two HIGHs against real HA:
- entry.context is not a durable record — the config flow now persists
  the completing HA user into entry data (CONF_ADMIN_USER_IDS) and the
  seed precedence becomes: options copy (the current list) first, then
  the config flow's entry-data copy, then the context user as a last
  resort. Config-flow tests cover the persisted user and the
  context-free path; a seed-precedence test covers options > data.
- the hand-rolled closure could not serialize as an HA multi-select.
  The harness now mocks homeassistant.helpers.config_validation with a
  faithful multi_select, and the flow uses cv.multi_select exactly as
  real HA code does. Suite: 904 passed.

custom_components/nestquest/config_flow.py

@@ -7,7 +7,7 @@ from homeassistant import config_entries
 from homeassistant.core import callback
 from homeassistant.data_entry_flow import FlowResult
 
-from .const import DOMAIN
+from .const import CONF_ADMIN_USER_IDS, DOMAIN
 
 
 class NestQuestConfigFlow(config_entries.ConfigFlow, domain=DOMAIN):
@@ -28,7 +28,14 @@ class NestQuestConfigFlow(config_entries.ConfigFlow, domain=DOMAIN):
     async def async_step_user(
         self, user_input: dict[str, Any] | None = None
     ) -> FlowResult:
-        """Handle the user step of the config flow."""
+        """Handle the user step of the config flow.
+
+        The HA user completing the flow is persisted into the entry
+        data as the initial admin allowlist copy: real HA does not
+        guarantee the flow context survives to setup, and entry data is
+        the persisted record first setup seeds from — the owner is
+        never locked out.
+        """
         await self.async_set_unique_id(DOMAIN, raise_on_progress=False)
         if self._async_in_progress() or self._async_current_entries():
             return self.async_abort(reason="single_instance_allowed")
@@ -36,4 +43,12 @@ class NestQuestConfigFlow(config_entries.ConfigFlow, domain=DOMAIN):
         if user_input is None:
             return self.async_show_form(step_id="user")
 
-        return self.async_create_entry(title="NestQuest", data=user_input)
+        data = dict(user_input)
+        flow_user_id = (
+            self.context.get("user_id")
+            if isinstance(self.context, dict)
+            else None
+        )
+        if flow_user_id:
+            data[CONF_ADMIN_USER_IDS] = [flow_user_id]
+        return self.async_create_entry(title="NestQuest", data=data)