Return the body of a send that saved nothing

Replaces the response-directory fallback with what the frontend already
does for ephemeral sends: the engine hands the body back, because it is
the only copy. Guessing at a file named for an id was the store reaching
around its own abstraction, and it is exactly what must not survive the
move to blob storage.

The send reply carries the bytes when the engine returned them, and the
runtime holds them for the rest of the call that sent them, so
ctx.httpResponse.body() answers for a saved and an unsaved response the
same way. Unsaved ones now report a real contentType too, taken from the
response the send already handed back.

crates-tauri/yaak-app-client/src/plugin_events.rs

@@ -7,6 +7,8 @@ use crate::{
     call_frontend, cookie_jar_from_window, environment_from_window, get_window_from_plugin_context,
     workspace_from_window,
 };
+use base64::Engine;
+use base64::prelude::BASE64_STANDARD;
 use chrono::Utc;
 use log::error;
 use std::sync::Arc;
@@ -53,13 +55,9 @@ pub(crate) async fn handle_plugin_event<R: Runtime>(
             .and_then(|window| workspace_from_window(&window).map(|workspace| workspace.id))
     });
 
-    // Same directory the engine writes bodies into, so responses it never
-    // recorded are still readable by id.
-    let response_dir = app_handle.path().app_data_dir()?.join("responses");
-
     match handle_shared_plugin_event(
         app_handle.db_manager().inner(),
-        &FileResponseBodyStore::new(app_handle.db_manager().inner(), &response_dir),
+        &FileResponseBodyStore::new(app_handle.db_manager().inner()),
         &event.payload,
         SharedPluginEventContext {
             plugin_name: &plugin_name,
@@ -319,8 +317,13 @@ async fn handle_host_plugin_request<R: Runtime>(
             )
             .await?;
 
+            // An ad-hoc request saves nothing, so the engine hands the body
+            // back and this reply is the only place the plugin can get it.
+            let body = http_response.body.returned_bytes().map(|b| BASE64_STANDARD.encode(b));
+
             Ok(Some(InternalEventPayload::SendHttpRequestResponse(SendHttpRequestResponse {
                 http_response: http_response.response,
+                body,
             })))
         }
         HostRequest::OpenWindow(req) => {