Improve /tabs completion workflow (#16168)

Follow-up of https://github.com/zed-industries/zed/pull/16154

Reworks /tabs arguments to allow:
* current tab by default, if no arguments are present
* fuzzy-matching over paths of the related tabs
* `all` case to insert all tabs at once

Release Notes:

- N/A

crates/assistant/src/slash_command/prompt_command.rs

@@ -2,7 +2,7 @@ use super::{SlashCommand, SlashCommandOutput};
 use crate::prompt_library::PromptStore;
 use anyhow::{anyhow, Context, Result};
 use assistant_slash_command::{ArgumentCompletion, SlashCommandOutputSection};
-use gpui::{AppContext, Task, WeakView};
+use gpui::{Task, WeakView};
 use language::LspAdapterDelegate;
 use std::sync::{atomic::AtomicBool, Arc};
 use ui::prelude::*;
@@ -32,7 +32,7 @@ impl SlashCommand for PromptSlashCommand {
         query: String,
         _cancellation_flag: Arc<AtomicBool>,
         _workspace: Option<WeakView<Workspace>>,
-        cx: &mut AppContext,
+        cx: &mut WindowContext,
     ) -> Task<Result<Vec<ArgumentCompletion>>> {
         let store = PromptStore::global(cx);
         cx.background_executor().spawn(async move {