Require /file or /tab when using Suggest Edits (#19960)

Now if you try to do Suggest Edits without a file context, you see this
(and it doesn't run the query).

<img width="635" alt="Screenshot 2024-10-30 at 10 51 24 AM"
src="https://github.com/user-attachments/assets/a3997ba6-98a9-4bfa-81b6-1d8579c26fd7">


Release Notes:

- N/A

---------

Co-authored-by: Antonio <antonio@zed.dev>

crates/assistant/src/prompts.rs

@@ -311,7 +311,7 @@ impl PromptBuilder {
     }
 
     pub fn generate_workflow_prompt(&self) -> Result<String, RenderError> {
-        self.handlebars.lock().render("edit_workflow", &())
+        self.handlebars.lock().render("suggest_edits", &())
     }
 
     pub fn generate_project_slash_command_prompt(