docs: update functions.fetch JSDoc to be more general

Updated the JSDoc comment to describe all use cases for the fetch method,
not just streaming. Now mentions custom HTTP methods, headers, raw response
access, and direct body control as additional reasons to use fetch over invoke.

Co-authored-by: Netanel Gilad <netanelgilad@users.noreply.github.com>

Author: claude[bot]

src/modules/functions.types.ts

@@ -82,8 +82,13 @@ export interface FunctionsModule {
   /**
    * Performs a direct HTTP request to a backend function path and returns the native `Response`.
    *
-   * Use this when you need streaming behavior (SSE, chunked text, NDJSON),
-   * because `invoke()` buffers the full response.
+   * Use this method when you need low-level control over the request/response that the higher-level
+   * `invoke()` abstraction doesn't provide, such as:
+   * - Streaming responses (SSE, chunked text, NDJSON)
+   * - Custom HTTP methods (PUT, PATCH, DELETE, etc.)
+   * - Custom headers or request configuration
+   * - Access to raw response metadata (status, headers)
+   * - Direct control over request/response bodies
    *
    * Requests are sent to `/api/functions/<path>`.
    *