docs: clarify build cache direct file transfer experiment

Author: Copilot

libraries/rush-lib/src/api/ExperimentsConfiguration.ts

@@ -148,8 +148,9 @@ export interface IExperimentsJson {
   /**
    * If true, the build cache will use file-based APIs to transfer cache entries to and from cloud
    * storage. This avoids loading the entire cache entry into memory, which can prevent out-of-memory
-   * errors for large build outputs. The cloud cache provider plugin must implement the optional
-   * file-based methods for this to take effect; otherwise it falls back to the buffer-based approach.
+   * errors for large build outputs and allow cache entries to exceed the limit of a single Buffer.
+   * The cloud cache provider plugin must implement the optional file-based methods for this to take
+   * effect; otherwise it falls back to the buffer-based approach.
    */
   useDirectFileTransfersForBuildCache?: boolean;
 }

libraries/rush-lib/src/schemas/experiments.schema.json

@@ -91,7 +91,7 @@
       "type": "boolean"
     },
     "useDirectFileTransfersForBuildCache": {
-      "description": "If true, the build cache will use file-based APIs to transfer cache entries to and from cloud storage. This avoids loading the entire cache entry into memory, which can prevent out-of-memory errors for large build outputs. The cloud cache provider plugin must implement the optional file-based methods for this to take effect; otherwise it falls back to the buffer-based approach.",
+      "description": "If true, the build cache will use file-based APIs to transfer cache entries to and from cloud storage. This avoids loading the entire cache entry into memory, which can prevent out-of-memory errors for large build outputs and allow cache entries to exceed the limit of a single Buffer. The cloud cache provider plugin must implement the optional file-based methods for this to take effect; otherwise it falls back to the buffer-based approach.",
       "type": "boolean"
     }
   },