server : enable multi-modal prompt caching (#19877)

tools/server/server-context.cpp

@@ -995,9 +995,6 @@ private:
             // don't update the cache if the slot's context is empty
             update_cache = update_cache && tokens.size() > 0;
 
-            // TODO: mtmd does not support prompt cache
-            update_cache = update_cache && (ret->mctx == nullptr);
-
             if (update_cache) {
                 SRV_WRN("%s", "updating prompt cache\n");
 

tools/server/server-task.cpp

@@ -1900,10 +1900,9 @@ server_prompt * server_prompt_cache::alloc(const server_prompt & prompt, size_t
         return nullptr;
     }
 
-    // TODO: for some reason we can't copy server_tokens, so we have to do this workaround
     auto & cur = states.emplace_back();
     cur = {
-        /*.tokens      =*/ server_tokens(prompt.tokens.get_text_tokens(), false),
+        /*.tokens      =*/ prompt.tokens.clone(),
         /*.data        =*/ std::move(state_data),
         /*.checkpoints =*/ prompt.checkpoints,
     };