Fix duplicate cache logging and add server cache API tests

- Remove redundant cache status logging in request() method that was
  duplicating the more informative log from attachCacheStatus()
- Add comprehensive tests for server cache API logic including:
  - shouldUseCache() behavior with instance and method-level settings
  - attachCacheStatus() behavior for attaching cache status to results
  - Cache bypass header injection for act/extract/observe requests
  - Cache status logging for cacheable methods

Author: cursoragent

packages/core/lib/v3/api.ts

@@ -877,19 +877,6 @@ export class StagehandAPIClient {
       },
     });
 
-    // Log cache status if present in response headers
-    const cacheStatus = response.headers.get("browserbase-cache-status");
-    if (cacheStatus) {
-      this.logger({
-        category: "api",
-        message: `server cache ${cacheStatus.toLowerCase()}`,
-        level: 2,
-        auxiliary: {
-          "cache-status": { value: cacheStatus, type: "string" },
-        },
-      });
-    }
-
     return response;
   }
 }