fix(stewardship): address review issues in feat/layer-stewardship

- steward_log_event (line 14): add println after let discard so the
  function's last expression is Void, fixing the type mismatch on a
  Void-declared function
- steward_get_mission (lines 40-43): remove non-Config fallthrough that
  allowed any Episodic/Working node to silently override the mission;
  only Config nodes are now authoritative
- steward_align signal_deceive (line 56): widen 'deceive the user' to
  'deceive' to catch variants like 'deceive users', 'deceive them', etc.
- steward_align signal_hide (line 57): tighten 'hide from' to
  'hide from the user' to eliminate false positives on legitimate inputs
  like 'hide from a background process' or 'hide from view'
- stewardship.elh: document that steward_log_event is an internal helper
  exported only because El has no access modifiers; callers should not
  invoke it directly

stewardship.elh

@@ -4,4 +4,7 @@ extern fn steward_get_mission() -> String
 extern fn steward_align(input: String, imprint_id: String) -> String
 extern fn steward_validate_imprint(imprint_id: String, tool_name: String) -> String
 extern fn steward_cgi_check(action: String) -> String
+// steward_log_event is an internal helper exported here because El has no access modifiers.
+// External callers have no business invoking this directly — use steward_align,
+// steward_validate_imprint, or steward_cgi_check, which call it at the correct points.
 extern fn steward_log_event(kind: String, detail: String) -> Void