fix(objectql): make the elevation pin's fake where-matcher refuse combinators

check:where-matcher flagged the fake driver's matches() in
engine-repo-execute-elevation.test.ts as a new silently-wrong WHERE matcher
(a $-prefixed combinator key would be read as a literal field name instead
of being rejected). Refuse it loudly instead, matching the exact idiom
engine-readonly-strip-caller-values.test.ts's own fake driver already uses.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0112hMx9hjJ9BgB28X97DS68

Author: claude

packages/objectql/src/engine-repo-execute-elevation.test.ts

@@ -43,7 +43,14 @@ function makeDriver() {
   };
   const matches = (row: any, where: any): boolean => {
     if (!where || typeof where !== 'object') return true;
-    return Object.entries(where).every(([k, v]: [string, any]) => row?.[k] === v);
+    return Object.entries(where).every(([k, v]: [string, any]) => {
+      // [check:where-matcher] REFUSE a combinator this fixture does not
+      // implement, rather than silently reading it as a field name — the
+      // exact fake-driver idiom `engine-readonly-strip-caller-values.test.ts`
+      // already carries.
+      if (k.startsWith('$')) throw new Error(`fake driver: unsupported operator ${k}`);
+      return row?.[k] === v;
+    });
   };
   let n = 0;
   const driver: any = {